061 - Experimental Pertussis

This is a pretty neat study, though it kinda makes me cringe. You’ll see why.

Whooping cough is a respiratory infection caused by the bacterium Bordetella pertussis, though apparently there was a lot of debate about the pathogen (bacteria or virus?) in the first half of last century. This study was designed in part to test that.

The other part was testing whether Louis Sauer’s vaccine made from B. pertussis could protect against the disease (which would be another indication of its bacterial cause). So how did it go?

H. and E.J. Macdonald, a physician husband and nurse wife team, intentionally exposed four healthy brothers aged 6 to 9 years to cultures from a separate whooping cough patient. These boys, it turns out, were their own sons. Now that’s dedication to science!¹

Two of the boys, the 9-year-old and one of the 8-year-old twins, had been vaccinated by Sauer 5 months before, and the other two (8 and 6 years) had not. None had any previous exposure to pertussis.

The team took a cough plate culture from someone with typical whooping cough and grew cultures from it on agar, checking under a microscope to make sure it was a pure culture. Half of the growth on this plate they suspended in saline solution, and then filtered it through a filter with pores small enough to remove bacteria from the solution, presumably leaving only viruses, if there were any. The other half of the growth they suspended in saline without filtering.

To start, they squirted a little of the filtered solution into the boys’ nose and throat, then quarantined them in a rural apartment with their mother (the nurse) for 8 weeks. They didn’t come down with any symptoms within 18 days, long enough for whooping cough to show up, so it didn’t seem to be some virus present in the culture.

So then after the 18 days, the team squirted some of the unfiltered suspension into the boys’ nose and throat. They aimed for about 140 bacteria total per boy. First the vaccinated results: neither of the two vaccinated boys had any symptoms or sign of whooping cough in the whole period of 38 days. Cultures from their throats and such were consistently negative.

On the other hand, the unvaccinated boys started coughing after only 7 days. Cultures were rated as ++++, which seems very positive, even from the beginning. Over the next few weeks, their fever and coughing increased in severity, they started whooping and vomiting food and mucus, stopped eating much, and had headaches. Seems pretty miserable. Then they got better, fortunately.

After recovering, the team tested the antibodies of all four boys, as well as two others each that were known to be immune or non-immune, and found that all were positive except the two known non-immunes.

So what could be concluded from this: as few as 140 cells is enough to cause an infection. B. pertussis is the agent that causes whooping cough. Seven days is the incubation period (at least here). Possibly also that the vaccine works pretty well.

On the other hand, it’s definitely a small sample size (2 patients in each group), and there was no blinding or placebo, but it gave very distinct results in a very controlled situation. All of them were known to have been exposed to enough pathogen to cause disease, and none could’ve been exposed from somewhere else. The populations were pretty matched too: two of the boys were twins, one vaccinated and one not. But one could argue that it’s not good enough.

As a minor question, I’m not even sure why they would’ve thought there would be any virus on the culture plate, unless they thought it were stuck to and replicating along with the bacteria or something…

And finally, the cringe-y part: this seems so unethical based on my understanding of standards for medical research these days, exposing children to a potentially deadly disease, but at least we can benefit somewhat from the results.

Some others agree with me in some ways and make observations:

"In...1933 the Macdonald husband-and-wife team performed an experiment on their four sons, from which they concluded that 'a filter-passing virus plays no role in the etiology of pertussis.' The wife, a nurse, sequestered herself with the boys in a rural apartment for eight weeks...Aside from proving that there are hazards in being born into a physician's family, and that B. pertussis could cause whooping cough, the findings did not really exclude the possibility of a direct or indirect role for viruses in the disease. It would have been a hardy virus to survive through two subcultures on agar medium."² [Though later studies confirm the result.]

"In 1933, Sauer vaccinated 2 of 4 brothers; all 4 brothers were then inoculated in the nose and throat with whooping cough bacillus. The 2 hapless controls (sons of a local physician) developed classic cases of whooping cough while their vaccinated siblings remained healthy."³

The four boys.
Source: National Library of Medicine, and Baker 2000³

Citations:

1. MacDonald, H. & MacDonald, E. J. Experimental Pertussis. The Journal of Infectious Diseases 53, 328–330 (1933).

2. Nelson, J. D. Whooping Cough — Viral or Bacterial Disease? New England Journal of Medicine 283, 428–429 (1970).

3. Baker, J. P. Immunization and the American Way: 4 Childhood Vaccines. American Journal of Public Health 90, 199 (2000).

A Note on Researching Vaccines (or anything else)

A lesson from my own experience: I've been looking at a lot of vaccine-related websites from both sides recently, for this blog and in general. Some provide lists of allegedly research publications that allegedly show some kind of problem with vaccines, some go through all those publications and allege that they are worthless and/or unrelated, and some are the same kinds of lists from the other side (that vaccines are safe and awesome).

And I've found that my feeling of the weight of the evidence depends on which kind of site I'm going through at the moment. If it's a list of allegedly anti-vaccine research, I feel the weight of the evidence is on that side. And vice versa.

Fortunately I recognize that making judgments and conclusions from such feelings would be highly biased and susceptible to error. It's not the number of studies that matters, but rather the quality and relevance, to make a fair, rational judgment of the evidence, one must go through it all and evaluate it all as objectively as possible.

Basically my point is, don't rely on feelings of which side has more evidence, because those feelings depend on what you have been exposed to (or even just been exposed to more recently), and you might've missed something. So instead of relying on feelings: compile, catalogue, and calculate, whenever possible.

060 - The Corrected Average Attack Rate from Measles Among City Children

Today’s post is not directly related to vaccines, but indirectly: it’s about measles epidemiology, or the observation of patterns of measles in populations over time; how many cases, in which ages, when it’s fatal, etc.¹

Specifically, A.W. Hedrich suspected that reports of measles cases in cities didn't always indicate the true level of measles that existed; the reports were incomplete. So he calculated a correction factor that should help health workers determine if their reports were complete, or estimate what the true rate might be.

The rate of measles varies seasonally, attacking more in winter than in summer (like the flu I guess), but it also cycles up and down in what’s called “epidemic swing,” as you can see in Figure 1 from the paper. Sometimes there could be 13 times more cases in one year than in the next.

Figure 1: Reported measles case rates. Baltimore, MD. 1897-1927. Hedrich 1930.

This is because in a high year, many people are infected and become immune naturally, so there aren’t as many susceptible people to be infected the next year. Levels of immunity might even be high enough to produce some herd immunity effect, where the virus can’t transmit from infected people to susceptible people, because the only contact between those groups is via immune people (who block the transmission). So that’s a low year. But as more people are born, the proportion of susceptible people rises until there’s another epidemic. That’s the natural cycle of measles, in cities at least.

This cycle made it difficult to compare between cities though, because obviously comparing a low year in one city to a high year in another would be inaccurate. So it’d be better to compare averages, say over ten years, to even out the variation.

Measles is pretty much a disease of childhood, or at least it was in pre-vaccine days in cities, because hardly anyone avoided it for that long, and generally one time is enough to be immune for life. (Not to say it can’t infect adults if they’re susceptible; see Panum's report on measles in the Faroes to see what the disease could do to a completely susceptible population.²) But in these days, almost everyone in cities had been exposed by age 15, so Hedrich decided that comparing case rates in people under 15 would be the best strategy. This was especially true because including those over 15 could introduce bias in cities that had a lot of immigrants from the countryside, who were often over 15 but still susceptible (since measles didn't spread as well in rural settings due to low population density), so that could inflate the case rate.

Hedrich compared some surveys of different cities, figuring out what proportion of the population had ever been exposed to measles by their 15^th birthday. It was pretty consistent between cities, countries, and over time that this proportion was about 95%.

Figure 2: Measles history rates by age. Hedrich 1930

So one might think, if reports of measles cases over different ages up to 15 don’t add up to 95%, they’re incomplete, and one can calculate a correction factor from that! But one thing this doesn't take into account is the children that have died before reaching age 15, either from measles or from other causes. The 95% figure is based on surveys of living children. So Hedrich looked at some data to see what measles mortality was and if it could affect the correction factor.

He found that in Baltimore from 1906 to 1915, measles killed about 4 out of every 1000 children under 15. The deadliest age was around 1 year old, with about 14 in 10000 dying from measles. This isn't necessarily indicating severity at these ages; it could be that the longer one lived, the more likely one had already survived measles.

Figure 3: Data from paper, figure I made. Deaths from measles per million people in Baltimore at a given age.

But anyway, this allowed calculation of the correction factor, and it turned out that fatal cases of measles didn't really affect it much. Though this wouldn't be the case with diseases that had higher mortality, or even sometimes measles epidemics that were especially deadly (like in Aberdeen, Scotland from 1883 to 1902, where the estimated death rate from measles was 2 of every 100 people; pretty scary).

Using this correction factor, Hedrich calculated with remarkable consistency that on average, 6.5% of city children under 15 get measles each year. He discusses a number of potential confounding factors that could introduce error but decides they don’t change the results significantly. So this could be useful for further study of measles epidemiology.

A number of later papers cite this one as important for later epidemiology, but I think some may have confused this paper with another of Hedrich's, since I didn't find what they say is there in it. Still, it’s interesting:

"Hedrick [sic] demonstrated, in Baltimore, that measles epidemics did not develop when the level of immunity was above 55 per cent. Though all the figures do not necessarily apply to urban areas, his findings do point out that considerably less than 100 per cent of the population need become immune before an epidemic is prevented or halted."³

"Based on the study of Hedrich (1930), Sencer et al. (1967) estimated that in Baltimore during the period 1897-1927 a level of immunity of 55 per cent was sufficient to prevent the development of epidemics."⁴

"The meticulous studies by A.W. Hedrich of measles diffusion in Baltimore from 1897 to 1927 formed the basis for epidemiological studies of measles for nearly 35 years. By carefully tabulating monthly measles rates and correlating them with the proportion of the population under fifteen years of age, Hedrich was able to develop a ratio of susceptible to immune children and thus account for fluctuations in the incidence of measles. It was determined that when the level of natural immunity exceeded 55 percent, the diffusion rate decreased. However, children escaping epidemics were still susceptible, and as more children were born, the number of susceptibles was augmented. Increased numbers of susceptibles led, in turn, to further epidemic fluctuations in measles."⁵

Citations:

1. Hedrich, A. W. The Corrected Average Attack Rate from Measles Among City Children. Am. J. Epidemiol. 11, 576–600 (1930).

2. Panum, P. Observations made during the epidemic of measles on the Faroe Islands in the year 1846. Bibiliothek for Laeger, Copenhagen 3R, 270–344 (1847).

3. Kogan, B. A. et al. Mass measles immunization in Los Angeles County. Am J Public Health Nations Health 58, 1883–1890 (1968).

4. Griffiths, D. A. The Effect of Measles Vaccination on the Incidence of Measles in the Community. Journal of the Royal Statistical Society. Series A (General) 136, 441–449 (1973).

5. Pyle, G. F. Measles as an Urban Health Problem: The Akron Example. Economic Geography 49, 344–356 (1973).

O723 - The Neurotropic Virus Diseases

Quote of interest:

"By comparison with the ephemeral effects of antiserum, the protection afforded by vaccination is relatively long-lived. The chief disadvantage of all methods of producing active immunity is the comparatively long time they require to lead to results. While the long incubation period of rabies permits the adoption of such procedure, in acute diseases such as poliomyelitis it is useless to think of vaccination when the patient or animal is already infected. It must be carried out beforehand in anticipation of the coming epidemic. And this means that in the case of a disease like poliomyelitis, which in this country [England] relatively seldom causes serious epidemics, it is very improbable that public opinion will ever be educated to the point of wholesale vaccination. But looking to the future and speaking quite generally, one would be inclined to forecast that in both human and animal medicine vaccination will ultimately prove of greater value than serum therapy."

Citation: Hurst, E. W. The Neurotropic Virus Diseases. The Lancet 226, 758–762 (1935).

059 - Small-Pox and Vaccination in the Light of Modern Knowledge

In this post, James McIntosh reviews some things about smallpox and vaccination against it.

Smallpox has been known to humanity since the 10th century, and to Europe since the 16th. People confused it with measles at first, and so thought it fairly mild, until it killed some royalty. Mostly it was only fatal in children (not that that's a good thing); 90% of deaths in epidemics were in children under 5. Mortality in people who caught it was typically 30-50%, which is very high for an infectious disease. And virulence seemed to be increasing through the 18th century, so people were excited about immunization.

Somewhat later, virulence seemed to shift toward older people and decrease over all, probably because of immunization, but also because another variety of the disease seemed to appear: called alastrim, or variola minor, the disease it causes is much milder than the original, even though they are almost histologically and serologically indistinguishable. Alastrim doesn't seem to make vaccination impossible (which it might if it induced an adequate immune response itself), but vaccination does prevent alastrim. But it did not replace smallpox, which still caused epidemics just as serious as before.

Regarding smallpox itself, McIntosh was uncertain whether Edward Jenner's original virus was really cowpox (vaccinia) or was rather an infection of cows with smallpox. I haven't read anything so far that does make a clear distinction between these possibilities. But in either case, it seemed safer than the practice at the time, which was called variolation: inoculating people with a little smallpox, which would cause disease but not as much as if they caught the disease unintentionally, and would induce good immunity. That practice sometimes didn't work out well, as you might expect.

So when Jenner's vaccination (from vaccinia) came along, the practice spread widely because it was safer and milder but just as good immunity-wise. Not completely safe though, as I mentioned before (040): post-vaccinal encephalitis was a serious side effect from vaccination, in which the immune system seemed to attack the nervous system, often causing paralysis and/or death. The incidence of this was 1 in 3555 recipients, or 1 in 31531 in children under 2, which isn't very many, but a lot more than would be preferable. McIntosh had some suggestions for avoiding this, but none he was very certain about: treating cases with serum from vaccinated people, maybe, or preventing it entirely by weakening the virus before vaccinating; this latter had the risk that it might be too weak to induce a good immune response. McIntosh thought it should be possible to standardize and minimize the dose as much as possible to let the body respond to it before it spread too much. I wonder how successful any attempts at that might have been.

Citation: Mcintosh, J. Small-Pox and Vaccination in the Light of Modern Knowledge. The Lancet 215, 618–621 (1930).

O712 - Poliomyelitis; a review of its natural history

One interesting quote:

"It can be postulated that, in regions where poliomyelitis is endemic and where epidemics do not exist or have but lately made their appearance (Japan), the native populations are immune as a result of early exposure to poliomyelitis virus. This is also reflected in the young age distribution of cases. As a possible mechanism for the production of this immunity, it has been observed that sanitary conditions are more primitive in endemic areas than in countries afflicted by epidemics; primitive sanitation would tend to promote constant general dissemination of virus leading to exposure at an early age and the development of active immunity. In countries where sanitation is good or improving, dissemination of virus is generally less, opportunities for immunization are proportionately decreased, and consequently there develops periodically a population ripe for epidemics.
"This hypothesis seems not unreasonable and deserves to be tested by investigations carried out in endemic regions with primitive sanitation for the purpose of determining: 1) the detectability of the virus in the population and environment, (2) the development of antibody in relation to age, and, 3) the number of different immunological types of virus and their relationship to strains isolated in countries where epidemics prevail."

Citation: Ward, R. Poliomyelitis; a review of its natural history. Pediatrics 1, 132–138 (1948).

058 - Immunity in Influenza: The Bearing of Recent Research Work

In 1939, people had already discovered the influenza virus, but there were still a lot of questions. For example, how can one distinguish between illness caused by this virus and very similar illnesses caused by many other things? And are all flu viruses the same? In this paper, C.H. Andrewes addressed these issues.

People had observed that major outbreaks tended to be the real flu, while minor outbreaks were typically something else. Andrewes called the former "epidemic influenza" and the latter "febrile catarrhs." Clinically, the real thing tended to be sudden in fever onset, and have more symptoms like headache and general achiness rather than the cough and sore throat characterizing other things. But there was a lot of overlap.

Mostly they tried to distinguish by infecting ferrets. The real flu tended to infect ferrets while the other stuff didn't. But it could've been possible to infect ferrets with more than one virus; it was hard to tell.

Serologically (that is, regarding the antibodies that bind to a virus), there seemed to be at least 4 different kinds of flu antigen. They hadn't found good ways to characterize these yet. Antibodies against one wouldn't bind as well, or at all, to another.

Regarding duration of immunity, they had found that in animals it lasted a few months, and Andrewes thought that duration seemed to correlate to body size, so it might last up to 1 year in people. Not sure if this is valid. But in any case, it declined over time, at least in ferrets.

In ferrets, subcutaneous vaccination worked for moderate immunity, not great. But moderate might be enough: humans wouldn't normally encounter very much flu at a time; and if it didn't prevent it completely, it could reduce the severity so that more people survived; and if people had some immunity already, it could increase it.

But studying immunity from vaccines is tough, because epidemics are infrequent and unpredictable. So people were trying to use antibody levels as a proxy. Some showed that antibodies and immunity correlated well, especially in ferrets, but it was unclear.

Andrewes tended to use a vaccine of virus inactivated by dilute formaldehyde. This seemed safer than a live attenuated vaccine, because a virus changed to be less virulent could always revert to become more virulent.

Lastly, he discussed the issue of when is best to vaccinate people. Epidemics in England were happening about every 4 years, but this wasn't reliable. Usually they happened in December or January, so the best time would be 1-2 months before, in October and November.

Citation: Andrewes, C. H. Immunity in Influenza: The Bearing of Recent Research Work. Proc R Soc Med 32, 145–152 (1939).

057 - The Progress of Work on Calmette's BCG Vaccine

The Lancet published an editorial in 1931 summarizing the different opinions about Calmette's BCG vaccine against tuberculosis. TB is a serious disease, so having a vaccine would be great, but not everyone agreed that the BCG was that great.

Calmette and those who supported him claimed the BCG was safe and effective. According to Calmette, 336,000 children in France and >1 million worldwide had been given the BCG over 5 years, and this had reduced mortalities from TB from 15.9% to 3.4% in children under 5. Even Calmette recognized that the BCG didn't provide permanent immunity, but he thought it was good enough to get children through the period of life where risk from TB is highest, in the early years.

Additionally, BCG supporters claimed that these bacteria, though still alive when used in vaccines, were safe and innocuous. They could produce lesions, sure, but no serious cases of tuberculosis. Many did animal studies that agreed with this claim.

On the other hand, many other medical practitioners and researchers found the claims more questionable. According to studies in cattle, guinea pigs, and monkeys, the BCG didn't seem that reliable in terms of safety or efficacy. Some of them thought they found animals dead from TB after inoculating with BCG, and some thought the BCG bacteria might increase in their virulence (ability to cause disease) after being grown in animals for long enough. And even previous studies on this blog found that Calmette's recommendations (feeding newborns BCG) didn't seem to work well, at least in animals (056).

So health professionals in Britain set up a special investigation of BCG, with not-great results. They decided that Calmette's good results could've been due to fallacies and biases and inadequate controls; for example, without blinding and placebo, it's possible that receiving the vaccine could've correlated with better care of the children in general, maybe because only cautious parents volunteered for the study or something. So hard to conclude anything. Also, some animal studies seemed to say it wasn't good, while others that it was.

Also there was a tragedy around this time in Lübeck, Germany. Many infants, 251, received BCG vaccine from the Pasteur Institute, but 67 of these soon died from tuberculosis. It turned out that what probably happened was some virulent Mycobacterium tuberculosis had been mixed with the BCG by accident. It was an awful thing that stresses the need for quality control. But it was interesting to see how different people interpreted it in different ways: some that BCG should not be used because of a risk of this kind of thing happening with any live attenuated vaccine (which makes some sense; if you don't have a good way to distinguish between strains, you can't test for contamination); and others (including Calmette) that this just shows that BCG was safe, because it was the fault of some contaminant, not the BCG itself.

But nevertheless, the Britain committee decided at this point that the BCG was still in the experimental phase, not ready for widespread use.

Citation: The Progress of Work on Calmette’s BCG Vaccine. The Lancet 218, 259–261 (1931).

056 - Immunological Studies in Tuberculosis VI. Resistance of Guinea Pigs Vaccinated with Bacillus Calmette-Guérin (BCG)

Today's topic: tuberculosis. This study's authors, Petroff and Steenken, Jr., think that recent (at that time) studies of TB vaccines, especially the BCG live attenuated kind, were too inconsistent and conflicting, possibly because they were done on humans for short periods of time. What they wanted was long-term animal studies. This seems like a controversial opinion, since animals aren't always good models, but they went with it.

Petroff and Steenken Jr. felt that the safety of BCG had already been established, so their goal here was to test its efficacy in preventing tuberculosis, and determine the best dose, route of inoculation, etc.

To do this, they did four experiments with groups of guinea pigs, inoculating them with live BCG or another attenuated strain called R₁ or a strain called H₃₇ killed with heat, or nothing (as a control). The inoculations in the first three experiments were either intraperitoneal (in the abdomen) or subcutaneous, and the scientists tested the immune response by seeing if the animals' skin was hypersensitive to TB proteins. Then, after 4-5 weeks, they infected the animals with live, virulent H₃₇ tuberculosis.

Over the course of 516 to 619 days, they looked at the extent of disease among the guinea pigs, as well as average survival time (though this was complicated by some animals dying of other diseases). In terms of extent of disease, it didn't seem like any of the vaccines was especially better than the others, but all seemed to help somewhat (control animals consistently died after 220-230 days, while vaccinated often lived more than 300). R₁ might've been slightly better than the others.

The fourth experiment was somewhat different: instead of using adult animals vaccinated by injection, they tested the recommendation of Calmette (the discoverer of BCG) of feeding the vaccine to very young guinea pigs. This didn't work out well; neither BCG nor heat-killed vaccine induced a hypersensitive response, and neither seemed to protect the animals against TB.

Not too great a study, but it shows some effect at least.

Citation: Petroff, S. A. & Steenken, Jr., W. Immunological Studies in Tuberculosis VI. Resistance of Guinea Pigs Vaccinated with Bacillus Calmette-Guérin (BCG). J Immunol 19, 79–92 (1930).

055 - Diphtheria—a Preventable Disease

Scroll down if you only care about the epidemiology, the exciting part.

Recap: Diphtheria is a bacterial respiratory disease spread by air or contaminated surfaces/objects. The majority of symptoms, if not all, are caused by diphtheria toxin, a particular protein produced by the bacteria. This means that inactivating the toxin prevents the disease.

This is the basis upon which the practice of treating diphtheria cases with antitoxin came about. Antitoxin, or a solution of antibodies against the toxin, could inactivate it and reduce symptoms when given at the right time. Not good for prevention though. So people were trying to immunize people with combinations of toxin and antitoxin—the toxin to induce an immune response to immunize patients against the toxin, and the antitoxin to prevent the toxin from causing harm. But this was risky.

Then came toxoid: an inactivated form of the toxin that still induced an immune response, more safely. Much better.

So in this report, four Canadian researchers at the School of Hygiene and Connaught Laboratories at the University of Toronto discuss how toxoid vaccination is the first really effective measure in preventing diphtheria in Canada. To quote from the introduction:

"Before the introduction of active immunisation against diphtheria, no substantial reduction in that disease was evident in the Dominion of Canada. Although diphtheria antitoxin was made freely available to practitioners by the public health authorities in almost all parts of the country, for prevention as well as for treatment, the morbidity-rates maintained their previous high levels.

"This is not to say, however, that all efforts at control—isolation of cases and quarantine of contacts, separate of other members of the family, and prophylactic antitoxin—were entirely barren of results. The recorded morbidity-rates of diphtheria are the resultants of different influences in different periods. For example, environmental changes, such as urbanisation of the population, with greater opportunities for human contact, might well have caused a real increase in cases if there had been no control measures; the wider use of laboratory services may have revealed cases otherwise undiagnosed; the use of public health nurses and school nurses may have resulted in more complete notification; and the changing clinical conception of the disease may have included cases of a kind that would not have been included in earlier years. While correction cannot be made accurately for such factors, their possible influence on recorded rates cannot be neglected in making comparisons."

 Between 1920 and 1924, diphtheria killed between 128 and 232 per million people in Canada, around 1600 deaths a year total. More than 40% of these deaths were in children under 5, and almost 80% in children under 10. Between ages 2 and 14, it was the chief cause of death, 15% of deaths. So, not good.

But then, in 1925, health workers in Canada decided that toxoid was adequately safe and effective, so Connaught Laboratories started making enough of it to vaccinate many Canadians. Not everyone can tolerate toxoid as well; some have a bad reaction to it, but these can almost always be distinguished using the Moloney test. These people are usually older and have been exposed to diphtheria more in the wild, but aren't always adequately immune despite this, so another dose of dilute toxoid is helpful and safe. Using this test, the risk from immunization was much lower.

The Schick test was often used to determine immune status, but it hadn't been standardized between countries, and different test methods gave different results, so no firm conclusions could be drawn. The authors here recommend another technique: titration of blood antitoxin (i.e. antibody response). I believe this is the technique used today.

They did some tests of immunity with different doses or preparations of toxoid: one to three doses of unmodified toxoid, or 1-2 doses of alum-precipitated toxoid (bound to aluminum as an adjuvant, I believe). They found that three doses of unmodified toxoid, just plain, worked better than alum-precipitated toxoid, in terms of antibody levels induced (titres), and also in terms of how long the antibody titres lasted after immunization (at least 2-3 years, it seemed). At least at first, those receiving three-dose toxoid had higher antibody titres than people who were naturally immune from exposure to diphtheria, though titres decreased over time. The rate of decrease does get slower though, so titres might level out, and re-exposure to diphtheria seem to increase them again.

Epidemiology
Now for the exciting part. They vaccinated 27,000 children in Toronto public schools, and left another 90,000 unvaccinated as controls. Some of the vaccinated had received one dose of toxoid, some two, and some three.

So from the 90,000 controls, they derived expected case rates: how many cases per 10000 or whatever that could be expected given the same exposure. And they found that, compared to these expectations, the actual number of cases they saw in the vaccinated children was always lower. For those who received 1 dose, the number of cases was 29% lower than expected; for two doses, 74% lower, and for three doses, an amazing 90% lower. Only 10% of the children expected to get sick actually did! And these results fit well with the antibody titres observed previously for these dosages.

Then for another 5 years, they brought the number of children vaccinated with 3 doses up to 47,000, and saw similar results: 87 to 97% fewer cases of diphtheria than expected, averaging 91% reduction. Protection did seem to decrease over time since vaccinated, as would be expected from the antibody titre patterns too.

After 1932, though, the amount of diphtheria going around was too low to have a good estimate of protection. The authors credit the toxoid vaccine with this decrease, with reason. Connaught Labs had made 3 million doses of toxoid over 11 years, and it wasn't clear how much of this was used, but it must've changed things a lot. Nothing before had helped this much, even when Canada made antitoxin available for free in 1916 and diagnostic labs had increased and such. The decrease was even greater than would've been expected for the number vaccinated, and the authors attributed this effect to herd immunity.

As an example, the city of Hamilton in Ontario had especially good results. Observe this graph:

Recall that the vaccine had been in increasing distribution starting in 1925. So for 30 years, the cases and deaths had been pretty steady, but then suddenly there was a steep decline with the vaccine. And in Hamilton, they had no deaths since 1930, at least up to this publication in 1938, and no cases since 1933.

Toronto was also doing pretty well; it went from 1640 cases per million in 1930 to 35 per million in 1934, and from around 65 deaths per year in the early 1920s to less than 10 between 1933 and 1937, with zero deaths in two of those years.

Other places in Canada offered free toxoid immunizations to their citizens, such as Brantford, who saw no diphtheria at all between 1931 and 1936. All provinces noticed a decrease in mortality due to widespread vaccination. Seems good.

The last question this paper addressed was that of herd immunity and asymptomatic carriers (those who might be immune enough to not get sick, but could still spread disease to others who were susceptible). Some suggested that many more might be in the latter camp, so spread might not decrease much at all.

However, some people tested a number of people from the population in the early 1920s and 30s, to see how many were positive for the bacteria. If immunization didn't prevent infection, only symptoms, then you would expect that the number of positive tests would be constant even as immunity increased. What they saw, though, was that about 1 in 10 cultures in the 20s was positive for bacteria, whereas very few carriers (fewer than 10) were found anywhere in the 30s, even when thousands of children were tested. So immunity does seem to prevent carrier status also.

Overall: It's difficult to find anything specific to criticize in this data. The differences between vaccinated and unvaccinated are so dramatic; it's pretty obvious that there is some effect. And since the vaccine seems to have been distributed for free by a public institution, at least some of the time, it's not a money question.

Of course, it's not really good enough to stand on its own as proof that the vaccine is worthwhile, I suppose. It's very light on details, like an overview, not going into many methods or diagnostic criteria or anything, or subject selection. In the epidemiology, which might've been like a clinical trial, but we don't know, because it doesn't say how the subjects were selected, or randomized, or if there were a placebo, or any kind of blinding. And they do say that the diagnostic criteria had changed over time, so it's difficult to compare across years. I suppose it's likely that the number of positive diagnoses would've increased with increasing sensitivity, rather than decreasing, but who knows?

So overall, it seems like it fits well into the pattern of research I've been finding up till now, that vaccines work well, but is not so great on its own.

Citation: Fitzgerald, J. G., Fraser, D. T., McKinnon, N. E. & Ross, M. A. Diphtheria—a Preventable Disease. The Lancet 231, 391–397 (1938).

054 - The Effect of Hemophilus influenzae suis Vaccines on Swine Influenza

Richard Shope and others already knew that it was possible to vaccinate against influenza using the influenza virus, in animals at least (049). But an important part of typical swine influenza was an infection with bacteria called H. influenzae suis, which often caused a secondary infectious pneumonia that could be fatal. Immunizing with this bacterium intranasally doesn't prevent the flu, but it seems to help when combined with the virus. It seemed like the bacteria needed help from the virus to get into the body and infect. So Shope wanted to know if it would help on its own when inoculated intramuscularly, into muscle.

So he took H. influenzae suis (henceforth "H.suis" for ease of typing) cultures, killed some of them with heat, and kept the rest alive as a live vaccine. He inoculated 8 pigs with the former, heat-killed ones, and 6 with the live, 3 injections each. He didn't see any side effects from the killed vaccine, but the live consistently caused a fever after the second injection.

After a week or two, Shope tested their immunity with flu virus plus bacteria. He observed them for a few days, and then killed and autopsied them.

All of them got the regular, virus-caused flu, of course. Of those that received the killed vaccine, only one seemed completely protected from the bacterial infection, with no H.suis found anywhere in its body. Another two had bacteria only in their upper respiratory tract, not their lungs, and the remaining 4 had bacteria in the lungs, but their pneumonia was not as severe as that of the 3 unvaccinated control pigs.

The live results were a big weirder. The 6 pigs got very sick when infected with flu, but recovered remarkably after only a day and then had no more than mild illness, compared to controls that had typical flu. All the pigs had bacteria in their respiratory tract, but only one had them in the lungs.

Shope also tested the antibodies in the pigs' serum before infecting them, and none of them had inactivating antibodies against flu or bacteria. Which doesn't necessarily mean they weren't immune.

So in conclusion, intramuscular H.suis, either killed or live, seems to affect the course of the flu but doesn't prevent it. The live seems slightly better at protecting after the initial severe reaction, but the reaction does make it seem less appealing, so it's not clear which is better.

Shope speculates that the severe reaction could be due to an allergic-type reaction to H.suis naturally in the lungs being quickly cleared out, but it's not clear why the killed vaccine wouldn't induce this also.

And he says that this study is just interesting, not practically very useful because there's already a virus-based vaccine that can prevent the whole flu, not just the bacterial part. This is not quite true, as we know, because H. influenzae in humans was a common cause of secondary pneumonia after the flu, so a vaccine against it is quite useful, especially because even today our flu virus vaccine is not super-great enough to depend on.

Citation: Shope, R. E. The Effect of Hemophilus influenzae suis Vaccines on Swine Influenza. J Exp Med 66, 169–175 (1937).

O469 - Advances in Vaccine Therapy

This isn't a full post, but I really liked this quote (whole section, really) from a review written by Alexander Fleming (who you'll recall is credited with discovering penicillin, not that it's particularly relevant here).

"The question whether or not an individual can be protected against epidemic influenza by means of a vaccine is one which is of the greatest importance in medical practice. This question leads to another, What is epidemic influenza? Before the great war we were quite content to think that it was infection by the influenza bacillus of Pfeiffer, and there is no doubt that in the 1918-19 pandemic this bacillus was present in practically 100 per cent of cases in England and France, and that it was responsible for much of the mortality. However, more recent work, especially at the Medical Research Council laboratires, has definitely established that the primary infective agent in epidemic influenza is a virus. This virus can be passed on in ferrets and mice, and can be cultivated in the incubator in chicken embryos still in the shell. It appears likely that mild influenza, such as the first wave of 1918 or the more recent epidemics, is to all intents and purposes a pure infection of the virus and that the serious and deadly epidemic of 1918-19 was due to a combination of this virus with a bacterium, especially the influenza bacillus.

"A very interesting influenza story comes from America. During and following the 1918 pandemic an epidemic of swine influenza appeared among the pigs in that country. This swine influenza is a serious and fatal disease, and has been investigated by Shope (1937) [054] more thoroughly than was possible in any human disease. Shope discovered that swine influenza was due to a combined infection with a virus and a bacillus practically identical with the influenza bacillus of Pfeiffer. If he infected pigs with a pure virus without the bacillus a transient fever resulted and all the pigs recovered; if he infected them with the bacillus alone practically nothing happened; but if he infected pigs with both the virus and the bacillus typical swine influenza resulted and the pigs died with pneumonia. Shope found that the pigs which had been given the pure virus and had recovered from the trifling infection that resulted were completely immune to fresh infection with the virus. He also found that inoculation of the pigs with vaccines made from the influenza bacillus gave some degree of protection against swine influenza, although it was not so complete as the protection with the virus.

"Here it will be seen that all the animals receiving the vaccine of the influenza bacillus suffered from a much milder disease than the controls, which had not been protected. This observation is of the greatest interest in view of the attempts made to prevent influenza in man with bacterial vaccines, especially those of the influenza bacillus. After the 1918 pandemic many papers appeared stating that such vaccines had conferred a degree of protection against influenza, but none of the figures given have satisfied statisticians. In view, however, of Shope's experimental results with pigs it appears that these claims were justified and that protection can be obtained by such bacterial vaccines.

"Attempts are at present being made to protect man against influenza by means of a vaccine of the influenza virus. The results on experimental animals have been successful, but the opportunity has not yet arisen for the final proof that it can protect man during an epidemic. It seems likely that in the near future it will be possible to obtain a virus vaccine which will give, either alone or in combination with the older bacterial vaccine, complete protection against epidemic influenza in the majority of the inoculated individuals."

Citation: Fleming, A. Advances in Vaccine Therapy. Br Med J 2, 99–104 (1939).

053 - Minor Points in Diphtheria Immunisation

Previously on the Diphtheria Vaccine Show (or whatever), we saw that toxoid (or inactivated diphtheria toxin) had good potential for immunizing safely, since an immune response against the toxin effectively prevents serious disease. People had been using mixtures of toxin with antitoxin antibodies, but this was risky, so inactivating the toxin just enough that it didn't cause disease but still induced an immune response was better. Also, something called the Moloney test, in which a small amount of toxoid was put under a patient's skin, could detect if an individual was likely to have a severe reaction to toxoid immunization. If so, they could receive a modified dose or something safer, such as a mixture of toxoid and antitoxin serum.

So the current study by H.A. Raeburn examined this question somewhat. He compared results of Schick and Moloney tests for a number of patients. Recall that the Schick test, in which a small amount of intact toxin was placed just under the skin, to see how a patient reacted, was a measure of the patient's immunity: if there was a very positive reaction, the patient was not immune (because they couldn't neutralize the toxin), and if negative, the patient was immune. The Moloney test seemed rather opposite: a positive reaction showed immunity, because the patient's immune system was overreacting to it and causing the reaction. But there was a lot of overlap between the tests, so worth doing both.

Giving a full dose of straight toxoid to a sensitive individual could cause very unpleasant reactions, including headache, vomiting, fever, and overall illness for three days, though recovery was likely I think. So the Moloney test was important, and effective, for avoiding such reactions.

However, mixing toxoid with antitoxin was not risk-free either, since the antitoxin serum often came from horses, so there were other components in it that could induce an immune response. So a person injected more than once with horse serum often developed serum sensitivity, kind of like an allergy probably. And since some diseases at that time, such as scarlet fever, could be treated best only with serum, using up a person's chance at risk-free serum treatment on diphtheria immunization wasn't always the best idea. That is to say, a person could usually count on one serum treatment being okay, the next being more risky, the third even worse, etc. So if possible, it was good to avoid using serum in combination with diphtheria toxoid, because then if the person later needed serum to treat scarlet fever or something, the risk of negative reaction was lower.

Raeburn did a small experiment to test this hypothesis, that toxoid-antitoxin led to higher toxin sensitivity. He tested the serum sensitivity of a number of subjects (using similar methods as with the Schick and Moloney tests), then immunized them either with straight toxoid or toxoid-antitoxin mix, and then tested their serum sensitivity again. Sure enough, more of those immunized with a toxoid-antitoxin mix exhibited serum sensitivity afterwards.

Finally, the best part of this study! Most of the papers I've read about diphtheria toxoid immunization have been focused on whether it could turn Schick-positive (non-immune) patients into Schick-negative (immune); that is, could it effectively induce an immune response? Which is important, but I haven't seen where people correlated this test status to actual immunity by doing epidemiology with diphtheria epidemics or anything like that. Maybe toxoid makes people Schick-negative but for some reason doesn't actually make them immune! Who knows?

But in this study, Raeburn actually does report the effects of a diphtheria outbreak in an immunized population. There were 120 subjects in some sort of house (maybe a hospital or prison or orphanage, it doesn't say), all immunized with toxoid. And there was an outbreak of tonsillitis going around, showing that it was possible and likely that all the subjects were exposed to contagious diseases that spread by droplets through the air, the way diphtheria spreads. But among these 120 vaccinated subjects, only two of them came down with the disease.

This isn't super-great data, since there's no control group, so we have no idea just from this how many we would've expected to catch diphtheria if none of them had been immunized. It seems likely that it'd be more than two, and there's probably some other data from the time period to give some idea, but I don't know where it is. So I'll be on the lookout for better studies in the future.

Citation: Raeburn, H. A. Minor Points in Diphtheria Immunisation. The Lancet 230, 621–623 (1937).

Historical Aside: An Inquiry Into the Causes and Effects of the Variolæ Vaccinæ, Or Cow-Pox

I found this writing by Edward Jenner recently, and also read it. It's actually sorta fun to read, with much more flowery language than you would find in any scientific or medical publication these days.

"The wolf, disarmed of ferocity, is now pillowed in the lady’s lap. The cat, the little tiger of our island, whose natural home is the forest, is equally domesticated and caressed. The cow, the hog, the sheep, and the horse, are all, for a variety of purposes, brought under his care and dominion."

If you've forgotten, Jenner is credited with discovering a vaccine against smallpox, by observing that farm workers who were involved with milking cows sometimes caught a mild disease called cowpox from the cows, and that those who came down with cowpox were thereafter protected from smallpox (a much more serious infection).

"It commonly happens that a disease is communicated to the cows, and from the cows to the dairymaids, which spreads through the farm until the most of the cattle and domestics feel its unpleasant consequences. This disease has obtained the name of the cow-pox.

"Morbid matter of various kinds, when absorbed into the system, may produce effects in some degree similar; but what renders the cow-pox virus so extremely singular is that the person who has been thus affected is forever after secure from the infection of the small-pox; neither exposure to the variolous effluvia, nor the insertion of the matter into the skin, producing this distemper."

In this article, Jenner presents a number of cases he has observed in support of this observation, including some children that he intentionally inoculated with cowpox. It's worth a read.

Something that makes it a little more interesting is the context of these observations. First, Jenner wrote that he always observed cowpox coming from a disease of horses' heels called "the grease," or from other cows with the pox. But there's a note from the editor in this article saying this hypothesis has since been shown incorrect. So not everything that Jenner observed was accurate.

Secondly, inoculating people with something related to smallpox was not something that Jenner invented. People had been introducing small amounts of smallpox into the skin (what Jenner here refers to as "variolous matter") in order to induce an immune response without a full-blown smallpox infection, for a while before Jenner. It tended to be unpleasant and somewhat risky, but usually preferable than catching smallpox the "natural" way. And if Jenner and other doctors of the time were right, the technique of introducing it into the skin mattered a lot in how safe it was. But what Jenner did contribute was using cowpox instead of smallpox for this inoculation, which was much safer. Henceforth this was called "vaccination," related to the Latin for cow (vacca), and the virus that caused cowpox was later called "vaccinia," though they didn't yet know what kind of thing it was yet.

I know back then there were plenty of negative feelings about vaccination (see here), but it seems like if something similar to what Jenner did were introduced today as an alternative to the modern vaccine schedule, many anti-vaccine people might be much more positively inclined toward it ("natural" immunity, no toxic ingredients, etc), which strikes me as sorta ironic.

052 - Vaccination Against Tuberculosis. Comparative Results Obtained with Koch's Bacillen Emulsion, Calmette's B.C.G., and the Caseous Vaccine of the Saranac Laboratory

BCG seems like a good option for vaccinating against tuberculosis, but not everyone was comfortable being injected with live, potentially pathogenic organisms. Especially people in the US and UK. So Hugh Kinghorn and Morris Dworski tried to develop another type of vaccine that was equivalent but more appealing, using killed bacteria.

They based their strategy, as far as I can understand, on the observation that tuberculosis often produces lesions in the lung full of caseous material, which probably also includes products of the pathogen that are harmful to the tissues, so incorporating this material into a vaccine could help protect both against the pathogen itself and its harmful products. They call this the "caseous vaccine."

So then they set off to test this new vaccine in rabbits and guinea pigs. In the first set of experiments, the caseous vaccine did much better than no vaccine at all protecting the animals, and even did better than Robert Koch's attempt to make a TB vaccine. In one group of animals receiving the caseous vaccine, 75% had no disease at all and the other 25% only had mild TB.

In another experiment with just the caseous and negative controls, 35% of the vaccinated had no disease (compared to 26% of the controls), while only 46% of the vaccinated and 74% of the controls had advanced tuberculosis. Kinghorn and Dworski speculated that the controls did so well because their living conditions were good.

Lastly, they compared their caseous vaccine to the BCG version in rabbits. Three groups of 15 animals each got the caseous, the BCG, or none. 89% of those receiving the caseous were protected from TB, compared to 78% from the BCG and 10% from neither. No animals from either vaccinated group had advanced TB, whereas 40% of the controls did. The rest had mild disease.

After about 1.5 years, they re-infected the surviving rabbits from this experiment with TB, to test if the immunity from the vaccines lasted that long. This time, only 17% that got the caseous, 50% that got the BCG, and 20% of the controls had no disease; 17% each of caseous and BCG groups had advanced disease, and 80% of the controls.

They also looked at whether BCG on its own, since it is a live organism, caused disease at all. But they only saw a couple mild lesions on a couple animals, and no other symptoms.

So it seemed like the caseous worked pretty well at first, but didn't last very long compared to the BCG. And neither is super-great, so the authors recommend not relying on the vaccine as the only preventative measure, which seems wise.

From this study, the caseous vaccine does seem potentially useful especially for people who are nervous about attenuated vaccines, but no future papers have cited this study and I've never heard of caseous vaccines, so it might be only a historical curiosity at this point. There's some pretty good animal data about the BCG here though.

Citation: Kinghorn, H. M. & Dworski, M. Vaccination Against Tuberculosis. Comparative Results Obtained with Koch’s Bacillen Emulsion, Calmette’s B.C.G., and the Caseous Vaccine of the Saranac Laboratory. Trans Am Clin Climatol Assoc 53, 1–14 (1937).

051 - Canadian Experience with BCG Vaccine

The BCG (or Bacillus Calmette-Guérin) vaccine (mentioned in 036) is an attenuated strain of Mycobacterium that seemed to work to immunize against tuberculosis, so it's pretty important, but people have always wondered about its effectiveness.

This publication was a short report about BCG usage in Canada, regarding the conclusions of a subcommittee evaluating the value of the vaccine. It claimed that in general, English-speakers (as opposed to, I suppose, French-speakers such as Dr. Calmette) were less optimistic about the vaccine.

However, there had been an 8-year study with 5,126 subjects in Montreal using the BCG vaccine. 582 of the vaccinated subjects had been exposed to tuberculosis from their family situations (not intentionally, of course), and another 500 unvaccinated controls in similar conditions had been exposed. These subjects were 1 month up to 7 years of age; those who died before reaching a month old were excluded because there were too many other causes of death in those, I think.

So overall, about 10 from every 100 of the vaccinated subjects died from any cause, while almost 20 from every 100 died of the unvaccinated. In the vaccinated, about 2 of the 10 deaths were from tuberculosis; in unvaccinated, the number was about 7 of the 20. These seem like good numbers (a 71% reduction in deaths from TB), though it's odd that all-cause mortality was so much different between the groups also. Seems like perhaps the two groups were not equivalent, but there aren't enough details to tell for sure.

The second question is whether the vaccine is safe, especially since it is a live organism (though attenuated). Some people had criticized it previously, but this article claims that they had mostly changed their minds, and all agreed it was safe. They don't show data, though, so who can say.

Overall they seem optimistic, but still have questions about how reliable and long-lasting the immunity is. Further studies are required.

Citation: Canadian Experience with BCG Vaccine. Can Med Assoc J 35, 196–197 (1936).

050 - Propagation of Rabies Virus in Tissue Culture and the Successful Use of Culture Virus as an Antirabic Vaccine

This was a short report about some researchers, Leslie Webster and A.D. Clow, who found a way to grow rabies virus in tissue culture. Previously, it had only been propagated in lab animals or isolated from wild/feral animals. Being able to grow it in a lab, one way or another, is important because that's how to make the vaccine to prevent or treat this almost-always-fatal disease.

As I have discussed in previous posts (040 and 043), injecting someone with animal brain tissue as a vaccine against rabies often worked, but the downside was that occasionally it induced an immune response against the vaccinee's own central nervous system, especially the myelin component, which could cause serious problems.

Webster and Clow claim that their method, described in this study, should be less risky in this regard, because it doesn't contain so much extra brain tissue. They didn't test this, though, at least not here, so I'm not sure how much to believe it, and here's part of why:

The method for growing rabies in culture that they devised involves keeping cells from mouse brains alive in monkey serum (the liquid components of blood), and inoculating that with virus. So it still involves mouse brain material. Probably not nearly as much though, or as many different kinds, so they could be right.

Anyway, it does seem like a good alternative to propagating the virus in whole animals. They report that they passed the virus through this culture over a series of 16 transfers, and it still worked fine as a vaccine or as a pathogen in animals at the end. If the virus weren't growing, each transfer would have diluted it more and more, until there was hardly any left after six transfers. So it seems clear that it's actually growing.

And they tried immunizing mice and ferrets with it, injecting it into their body cavities, and it protected all of them from infection with virulent forms of the virus even when injected directly into the brain. Immunization by virus under the skin didn't really work though, at least in ferrets. But the immunizing power of this tissue culture virus seemed about as strong as that taken from animal brains. So it's pretty promising, perhaps.

Citation: Webster, L. T. & Clow, A. D. Propagation of Rabies Virus in Tissue Culture and the Successful Use of Culture Virus as an Antirabic Vaccine. Science 84, 487–488 (1936).

049 - Immunization Experiments with Swine Influenza Virus

Now for something different: influenza. By 1936, people knew that the disease was viral, not bacterial, though bacterial infections often complicated flu, causing even more sickness. So searching for a way to prevent the viral disease in the first place was a good idea.

Richard E. Shope took advantage of earlier studies of influenza in animals, and tested the possibility of immunizing animals against the flu by injecting them with the virus. No killing or inactivating at all, just injecting the live virus into muscle or skin or other areas of the body, apparently is enough to safely generate an immune response.

This was already known, but what Shope intended to test with this study was whether flu virus that had been cultured in one kind of animal (pig, ferret, or mouse) could provide immunity to another type. As secondary goals, he was looking at dosage and route of inoculation (either subcutaneous, under the skin, or intraperitoneal, into the body in the spaces between organs).

The flu Shope used had been isolated from swine originally, but in the lab he had passed some of it through mice and some through ferrets, so those strains were adapted to those animals. He used infected lung tissue from each animal, ground up and dissolved in saline, as vaccines and infecting doses.

First he tested seven pigs, inoculating them with virus from pigs, ferrets, or mice either subcutaneously or intramuscularly. Then, along with two non-immune controls, he infected them with virus through the nose. After 4 days, Shope killed the pigs and examined their lungs for flu lesions and their blood for anti-flu antibodies.

And all seven turned out to be immune, while the controls got sick. One of the seven pigs had live virus in its nose, but none had it in their lungs, where the infection is worst. And they all had antibodies against the virus.

Next he tried ferrets, inoculating them subcutaneously or intraperitoneally. The 8 controls all had severe illness with virus easily found, but those immunized with ferret-derived virus were immune, all except one out of nine. Of those inoculated subcutaneously, all the ferrets immunized with swine or mouse virus got sick, but intraperitoneal inoculations from those animals seemed better able to protect (66% from swine, 100% from mice).

Finally was the test in mice, which apparently are a useful model because the virus kills them easily but doesn't really spread between them, so strict isolation is not necessary. The setup was pretty much the same as with the ferrets. In this case, 79 out of the 83 control mice died within 7 days after infection, as expected.

Of those immunized with mouse virus, 77 out of 99 immunized with two large doses survived, about equal proportions subcutaneous or intraperitoneal (it didn't matter), though only 29 out of 68 given one large dose survived, and 42 out of 83 given two smaller doses.

Of mice given swine or ferret virus subcutaneously, only 8% survived from swine virus and 17% from ferret. Intraperitoneal injection was better: 70% from swine, especially with a higher immunizing dose, and 67% from ferret.

Since it is a live virus vaccine, Shope monitored the inoculated mice for illness, and a few did die, but mostly from intestinal infections. A very few did die from pneumonia, but he wasn't able to find any flu virus present in these, so it could've been something else.

These results are promising, but Shope also presents some data that are more troubling. Some pig farm in Iowa had done an experiment with this sort of vaccine, immunizing more than 1500 pigs. Mostly the vaccinated were kept separate from the others, but in a few droves that was not possible. In one drove of 223 animals, 23 were vaccinated, and soon after, a flu infection broke out in the drove, infecting all but 30 (including 20 of the vaccinated). There were no other infections going on in Iowa at the time, and it was too early in the season for flu to be going around, so Shope suspected that it came from the inoculation somehow. A similar thing happened in another drove.

So it seems that live virus in body tissues can generate a protective immune response, especially if the virus originates from the same kind of animal (except in pigs, who can gain immunity from any virus apparently). And it's possible that with this type of vaccine, other susceptible individuals in the environment may be at risk of infection from the vaccinated. So it's promising, but not quite ideal.

Citation: Shope, R. E. Immunization Experiments with Swine Influenza Virus. J Exp Med 64, 47–61 (1936).

048 - Poliomyelitis Following Vaccination Against This Disease

This one is pretty short, but important. And closely related to the previous two posts (046 and 047). In this short article, J.P. Leake of the U.S. Public Health Service lists twelve cases of paralytic polio in children, but not just any polio.¹

As you may recall from the previous posts, there were a couple of experimental polio vaccines being tested around this time, and more than 11,000 people had received them. Brodie’s was allegedly completely inactivated, and Kolmer’s was still alive, but chemically attenuated enough that it rarely caused problems in monkeys. But when it is uncertain whether a given person will ever encounter the virus, let alone have a serious reaction to it (such as paralysis or death), any vaccine must be extremely safe in order to be worth giving to the whole population.

Brodie and Kolmer claimed their vaccines were so safe, but Leake presents evidence to the contrary (though without naming names). His report of 12 cases come from children aged 5 months up to 20 years. Six of these children died from their polio, and at least four were still paralyzed at the time of this study. And more importantly, they all came down with symptoms one to two weeks after receiving a dose of experimental vaccine.

By itself, this wouldn’t mean much, since they could’ve been exposed to the virus soon before (or soon after) receiving the vaccine, such that they came down with symptoms before immunity set in. But in these cases, they weren’t in areas where polio epidemics were happening, and they hadn’t been exposed to people from known epidemic areas. Even worse, their paralysis tended to begin in the same area of the spine where they had received the dose of the vaccine (which in itself was pretty interesting, as it implied that the virus travels through nerves rather than other bodily networks).

So it seems like these unfortunate children were infected by an improperly-prepared product. As Leake concludes:

"Although any one of these cases may have been entirely unconnected with the vaccine, the implication of the series as a whole is clear."¹

Of the studies that cite this paper, almost none disagree with its conclusion, though a few try to propose an alternative explanation (that the vaccine interfered with an immune response to an already-ongoing polio infection, for example). But a couple reviews summarize the history well:

"The Kolmer vaccine was known to contain a small amount of live virus capable of infecting monkeys, but it was presumed to be safe for humans on the basis of the unproved assumption that serial passage in monkeys had reduced its pathogenicity for man. This vaccine was clearly implicated as the cause of a number of cases of poliomyelitis. The Brodie vaccine, believed to be completely inactivated, was also suspected of causing several cases of poliomyelitis, but the evidence is much less convincing. At a meeting of the American Public Health Association in November 1935, reports were given on both vaccines. During the discussion of these reports, both vaccines were roundly condemned, particularly by Rivers of the Rockefeller Foundation and by Leake of the U.S. Public Health Service. Shortly thereafter, Leake published a list of vaccine-associated cases, and the vaccines were withdrawn from use."²

"Undaunted, Brodie fooled himself and convinced Park that the vaccine was safe, attempting to prove it by inoculating himself, Park, and a few laboratory technicians, after he had done a group of monkeys. He presented and published papers, invoking Park's name and cajoling him to serve as cosponsor. The Brodie-Park vaccine was thereby launched and the press began to take notice. Their enthusiastic coverage of events aroused the hopes of parents and physicians anxious to believe that protection from the crippling scourge might at last be at hand.

"Meanwhile, a competitor, John A. Kolmer of Philadelpha, called a press conference to announce that he had successfully tested a vaccine, different from Brodie's in that the virus in his vaccine was "live but devitalized," the attenuation achieved by the addition of sodium ricinoleate. In addition, Kolmer's vaccine was carried one step further, having been tested not only in monkeys and on himself and his two children but also on 22 other children. Reporters asked Park whether his vaccine also was ready for human use. Brodie had assured him it was and that tests on children were planned. The press whipped up the rivalry to the point where newspapers carried frequent progress reports resulting in antics in which each tried to outdo the other.

"The pressure of public expectation, the lack of restraint, and poor judgment soon forced both Brodie and Kolmer to undertake the inoculation of several thousand children under the poorest of circumstances for such an experiemnt. The experiment resulted in at least 12 vaccine-associated cases and six deaths. Another tragic incident, another immediacy, and the U.S. Public Health Service stepped in, ordering that both of these vaccines be withdrawn and destroyed. With this were sown the seeds for the stringent legal requirements for vaccine safety and efficacy which were to sprout some years in the future."³

 Citations:

1. Leake, J. P. Poliomyelitis Following Vaccination Against This Disease. Cal West Med 44, 141–142 (1936).

2. Meier, P. Safety Testing of Poliomyelitis Vaccine. Science 125, 1067–1071 (1957).

3. Schaeffer, M. William H. Park (1863-1939): His Laboratory and His Legacy. American Journal of Public Health 75, 1296 (1985).