002 - Observations on vaccination and small-pox, more especially with reference to the theory of vaccine influence, and the relations subsisting between the cicatrix and the character of the consecutive variola

Another old one, this time from 1841. These old publications are amazingly wordy and flowery! But now we get into some actual interesting data.

As in the previous article, the "vaccination" in this paper refers to inoculating patients with cowpox, also known as the vaccinia virus, pretty much by taking some infected pus from a previous patient and scraping it into a new patient's arm with a needle. This resulted in a mild infection that gave the immune system enough of a recognition of smallpox (variola virus) that it could respond and prevent the latter from being quite as deadly. Remember, smallpox could kill up to 80% of people it infected (I am happy here to be able to use the past tense when referring to it).

The author is a physician at the Smallpox Hospital in London, reporting on an epidemic of smallpox in 1840. Apparently between January 1839 and September 1840, there had only been about 16 cases each month, but then an outbreak started that resulted in almost 16 cases every four days. He gives some statistics about the cases he observed that year.

• 61% of cases had not been vaccinated
• Of these, 45% died
• 38% had been vaccinated previously
• Of these, 7% died
• 1% had had smallpox before

Here's a graph:

Seems like a big difference to me. But it is possible to question how many people of each group got sick enough after being infected to need to go to the hospital, and how many people in the general population of each group got infected at all. All we know is the case:fatality ratios.

Also potentially of interest are the effects on different age groups, of all patients (vaccinated or not):

• 15% were under 5 years old
• 60% of these died
• 14% were 5 to 15 years
• 20% of these died
• 71% were over 15
• 26% of these died
• Overall, 30% of patients died

What the author does report about vaccinated patients is the following: only 9% of those who had been vaccinated were under 16 years, and none were under 5 years (though occasionally a younger vaccinated child did catch it).

Other than that, the rest of the report is arguing that the appearance of the scars on the arms from vaccination  doesn't correlate well with how well-protected an individual is from smallpox. The author gives a series of cases in which nice-looking scars gave little protection and not-nice ones gave good protection.

Overall, it seems like good evidence, for what it's worth, that vaccination helped moderate the severity of smallpox.

Citation: Gregory, G. Observations on vaccination and small-pox, more especially with reference to the theory of vaccine influence, and the relations subsisting between the cicatrix and the character of the consecutive variola. Med Chir Trans 24, 15–29 (1841).