071 - The Immunization of School Children Against Whooping Cough

In addition to the Sauer vaccine, which used whole bacterial cells to prevent whooping cough, others had developed the Krueger vaccine, which was made from bacterial cells broken up mechanically and then filtered thoroughly so that only the soluble cellular components remained. Basically this was an acellular version, intended to be less likely to cause serious reactions in subjects, but still induce a good immune response because the important parts were still there.

So Frawley had been testing this vaccine in school-aged children, not younger, reasoning that the disease mostly passed through a population in schools, so preventing transmission in schools could prevent children from bringing it home to younger siblings. Apparently in Fresno, where this study took place, 70% of school children hadn't had pertussis yet.

The first trial was in January 1933, 345 children, but it didn't seem to help much in the following pertussis outbreak, because only a very small dose was given. So in November they did another trial with 505 children, with a larger dose.

During the time of the trial, 80 vaccinated children were exposed to pertussis, but only 31 of them got sick; 61% were protected. These were mostly only mildly sick, with a short duration of the characteristic cough; 25 coughed for less than a week, and only 1 for more than 2 weeks.

There was no control group to compare how many unvaccinated got sick, but Frawley did observe a group of 174 unvaccinated children who did come down with the disease, to see if they had it worse than the sick vaccinated group. It seemed so: only 9 of the 174 (5%) coughed less than a week, while 116 (67%) coughed more than 2 weeks. So it was a pretty big difference in severity, by that measure.

Frawley noted that the vaccinated subjects didn't have any serious reactions, though some who had had pertussis recently had more serious local reactions, possibly allergic. Not very serious though. He also noted that these reactions stopped when the pertussis had happened more than a few years before, indicating fading natural immunity.

Overall, the results are interesting in the difference in disease severity, but it wasn't a very well-controlled study, so not much can be concluded.

Reference: Frawley, J. The Immunization of School Children Against Whooping Cough. JAMA 103, 960–962 (1934).