While studying the clinical modification of whooping cough by the use of alum-precipitated diphtheria toxoid, I had the opportunity to observe 9 children exposed to siblings with pertussis who were inoculated with this toxoid at the time the siblings began to cough or before, and who were protected from whooping cough in spite of the fact that they continued to live with the siblings who had the ailment. This fact at the time (1943) seemed significant, although not conclusive, and induced me to institute observations of other exposed persons under the same circumstances. The fact that the latter subjects obtained protection by inoculation with alum-precipitated toxoid supported the idea suggested by the first 9 cases.
Up to the present time I have observed 61 exposed children under conditions that do not warrant the slightest doubt that opportunity for contagion existed, since all of these children lived in the same houses
TURNBULL JM. ALUM-PRECIPITATED DIPHTHERIA TOXOID FOR INOCULATION OF PERSONS EXPOSED TO WHOOPING COUGH. Am J Dis Child. 1945;69(1):5-6. doi:10.1001/archpedi.1945.02020130012002