020 and 021 - Results of Prophylactic Vaccination Against Pneumonia at Camp Wheeler

In terms of time, people, and purpose, this post is a continuation of 017: published a year later, performed by at least one of the same authors, and as a follow-up to the previous. Also subject to many of the same comments and criticisms.

So, the Cecil & Vaughan article is the study itself, and the other is basically a review of it with some policy recommendations. While 017 took place in Camp Upton, NY, this took place at Camp Wheeler, Georgia. This camp had been having serious trouble with pneumonia, and 34% of it was from pneumococcus types I-III, against which Cecil & Co could vaccinate. And they did.

The vaccine in the previous study was a suspension of killed bacteria in salt solution, which seemed to cause more irritation and side effects than the authors felt it should, so in this study they tried to improve it by instead suspending the bacteria in vegetable oil. Apparently others had good results with this method, decreasing the dose volume and number of injections while maintaining good immune response, with lower irritation to the recipient.

So Cecil and Vaughan gave this vaccine to a total of about 13460 men in the camp, leaving 3415 unvaccinated. It did seem to be less mild, with only 37 out of 100,000 recipients suffering the strange infiltrations that were common with the saline vaccine (1214 of 100,000). Only 7 in 1000 men had to stay in the hospital for a few days, and 77% of these had received another bacterial vaccine at the same time as the pneumococcal one. Still, this seemed more severe than it needed to be.

Now the results. I'm going to share the graph they put in the paper, since I can:

This shows that the vaccination rate rose over time (as they vaccinated more of the troops), and partway through they got a surge of new recruits. Then there was a spike of pneumonia in the unvaccinated troops, but much less in the vaccinated.

Here are graphs I made, similar to those in 017 except without a breakdown of different causative agents:

There were many fewer cases of both pneumococcus and overall pneumonia. Actual numbers were 42 of types I-III in the 3415 unvaccinated troops, vs. 8 in the 13460 vaccinated (actually there were 32 cases, but 24 of those happened within a week after vaccination, and work by another author showed that immunity is not present until 8 days after vaccination, so those were excluded).

Overall, for all types of pneumonia, there were 327 cases in 3415 unvaccinated, and 155 in 13460 vaccinated.

Death rates are proportionally similar:

Numbers for types I-III are 1 in 13460 vaccinated vs. 14 in 3415 unvaccinated.

This study was complicated by a few things, though, which make the results more difficult to interpret. Most importantly, the 1918 flu pandemic arrived about the middle of this study, making the risk of secondary pneumonia much greater. Second, the number of men in the camp was changing, with new recruits (more susceptible to pneumonia) coming in and other troops leaving, so it was difficult to say how much effect vaccination had on each group. Still, the populations did seem decently equivalent.

And so, like in 017, it's difficult to explain why the vaccinated troops seemed to be well-protected even from types of pneumonia against which they weren't vaccinated. The authors speculate there could be cross-protection, providing some protection against multiple different pathogens, but it is not clear. And again, how long the protection against pneumococcus might last after vaccination was not determined, so it might not be very long. So again, medium quality (relative to other studies I've written about so far, at least).

Russell Cecil seems to agree, acknowledging that his pneumococcus vaccine was not good enough for a population-wide vaccination effort (because of its limited cross-protection, still-too-unpleasant side effects, and the fact that pneumonia doesn't really cause awful outbreaks like smallpox did). But he did recommend it for certain high-risk populations, such as soldiers, miners, people in institutions, and those individuals that seemed especially susceptible. But I believe there is more improvement to be made.

Citations:
Cecil, R. L. Present Status of Pneumococcus Vaccine. Am J Public Health (N Y) 9, 589–592 (1919).

Cecil, R. L. & Vaughan, H. F. Results of Prophylactic Vaccination Against Pneumonia at Camp Wheeler. J Exp Med 29, 457–483 (1919).