This is a follow-up to an interim report on a big trial of whooping cough vaccine (065). That report didn't show much difference between vaccinated and unvaccinated, and this final report doesn't improve things much. This is weird, because other big trials at the time that showed pretty positive results (072). There was some suspicion that it was the preparation of the vaccine that made the difference, but that didn't seem to be true (093), so it's pretty mysterious.
So in this final report, the proportions of subjects in each group that got sick were about 15% in the vaccinated and 19% in the unvaccinated controls. Allowing an extra three months before starting to count cases (to let immunity develop after vaccination), the numbers were 16% and 18%, so no better.
The average severity between groups might've been different though. For one thing, there was one death in the control group and none in the vaccinated, but that's not enough to make any conclusions. But apparently multiple people reviewed whatever records they had about severity and came to the same result, that the proportion of mild cases vs. severe cases was higher in the vaccinated group: about 59% mild in vaccinated vs. 35% in controls, and 0% severe vs. 3.5% in controls. But it could've been more rigorous in record-keeping.
So overall, not promising results, but not nothing. Why it differed so much is still mysterious. One interesting thing to note is from this other study that compared several large trials at the time, the attack rate of unvaccinated subjects in Doull's study seemed a lot lower than in others (about half) for some reason.2
Though other reviews seemed to think that this was one of the best studies of the time:
References:
So in this final report, the proportions of subjects in each group that got sick were about 15% in the vaccinated and 19% in the unvaccinated controls. Allowing an extra three months before starting to count cases (to let immunity develop after vaccination), the numbers were 16% and 18%, so no better.
The average severity between groups might've been different though. For one thing, there was one death in the control group and none in the vaccinated, but that's not enough to make any conclusions. But apparently multiple people reviewed whatever records they had about severity and came to the same result, that the proportion of mild cases vs. severe cases was higher in the vaccinated group: about 59% mild in vaccinated vs. 35% in controls, and 0% severe vs. 3.5% in controls. But it could've been more rigorous in record-keeping.
So overall, not promising results, but not nothing. Why it differed so much is still mysterious. One interesting thing to note is from this other study that compared several large trials at the time, the attack rate of unvaccinated subjects in Doull's study seemed a lot lower than in others (about half) for some reason.2
Though other reviews seemed to think that this was one of the best studies of the time:
"Doull...took particular care to avoid the numerous pitfalls that attend trials carried out in a clinic population...The same cannot be said of many of the apparently successful trials."3It'll be interesting to see why the positive studies overwhelmed this kind of result, such that now pertussis vaccine is so common.
References:
1.
Doull, J. et al. Active immunization against pertussis: Final report on the cleveland immunizations of 1934-1935. Am J Dis Child 58, 691–698 (1939).
2.
Perkins, J. E., Stebbins, E. L., Silverman, H. F., Lembcke, P. A. & Blum, B. M. Field Study of the Prophylactic Value of Pertussis Vaccine. Am J Public Health Nations Health 32, 63–72 (1942).
3.
Vaccination against Whooping-cough. BMJ 2, 222–223 (1945).
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