This is another trial of a pertussis vaccine, similar to the others. The justification was that whooping cough is contagious before it is easily recognizable, so it's hard to prevent by anything but immunization.
The subjects were children of 6 to 30 months old, most under 1 year. They were selected from those attending the Stanford Well Baby Clinic randomly, and controls were chosen randomly from the same group, so it was pretty well randomized (except that presumably the parents in the vaccine group had to agree to the vaccine).
The vaccine was whole killed bacteria, a normal dose like Sauer's, 3 doses each a week apart. They started counting after the last dose was given, to make sure everyone was fully immunized. From these shots, they saw 4 systemic reactions, which were just a day of fever.
Then they got the parents to inform them of any known cases of pertussis, and any exposures to others with pertussis. These were diagnosed either by the typical coughing symptom or by culturing the bacteria on cough plates. Some had neither but were counted as "probable" because of history of exposure.
Results
Over the 2.5 years of the study, the vaccinated group had 26 exposures resulting in 7 cases (2 of which were questionable). So the infection rate was 26.9%.
The controls had 25 exposures resulting in 22 cases (1 questionable), so 88% infection rate. The difference between the two groups was statistically significant, both in infection rate and attack rate (the proportion of all subjects infected vs. not), so it seemed like the vaccine was protective.
The control group had 11 cases from unknown exposures, and the vaccinated group had only one, so it's possible to assume the vaccinated group actually had 10 more unknown exposures that would otherwise have resulted in disease, lowering the infection rate to 23%.
In terms of severity, the vaccinated cases were never severe; a few were typical, some mild or questionable. The control cases were mostly typical, 3 severe, 5 mild or questionable. So the vaccine seemed partially protective even in those that got sick.
In terms of immunity duration, of those that got sick in the vaccinated group, most had been vaccinated over 1.5 years before, so the authors recommend small yearly boosters.
Overall, not as rigorous as possible, but pretty good, and the vaccine was helpful but not super-great.
Reference:
The subjects were children of 6 to 30 months old, most under 1 year. They were selected from those attending the Stanford Well Baby Clinic randomly, and controls were chosen randomly from the same group, so it was pretty well randomized (except that presumably the parents in the vaccine group had to agree to the vaccine).
The vaccine was whole killed bacteria, a normal dose like Sauer's, 3 doses each a week apart. They started counting after the last dose was given, to make sure everyone was fully immunized. From these shots, they saw 4 systemic reactions, which were just a day of fever.
Then they got the parents to inform them of any known cases of pertussis, and any exposures to others with pertussis. These were diagnosed either by the typical coughing symptom or by culturing the bacteria on cough plates. Some had neither but were counted as "probable" because of history of exposure.
Results
Over the 2.5 years of the study, the vaccinated group had 26 exposures resulting in 7 cases (2 of which were questionable). So the infection rate was 26.9%.
The controls had 25 exposures resulting in 22 cases (1 questionable), so 88% infection rate. The difference between the two groups was statistically significant, both in infection rate and attack rate (the proportion of all subjects infected vs. not), so it seemed like the vaccine was protective.
The control group had 11 cases from unknown exposures, and the vaccinated group had only one, so it's possible to assume the vaccinated group actually had 10 more unknown exposures that would otherwise have resulted in disease, lowering the infection rate to 23%.
In terms of severity, the vaccinated cases were never severe; a few were typical, some mild or questionable. The control cases were mostly typical, 3 severe, 5 mild or questionable. So the vaccine seemed partially protective even in those that got sick.
In terms of immunity duration, of those that got sick in the vaccinated group, most had been vaccinated over 1.5 years before, so the authors recommend small yearly boosters.
Overall, not as rigorous as possible, but pretty good, and the vaccine was helpful but not super-great.
Reference:
Miller, Jr., J. J. & Faber, H. K. Immunization against pertussis. JAMA 112, 1145–1148 (1939).
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