During the last four years, several epidemics of pertussis have occurred in a large institution for the care of children harboring about 400, ranging in age from 1 day to 6 years. The opportunity was thus afforded us to study the disease with special reference to (a) natural immunity, (b) acquired immunity, and (c) the diagnosis of the disease in its earliest stages, and before the onset of the characteristic spasmodic cough, whoop and vomiting.
Children exposed in previous epidemics and not acquiring the disease were considered as possessing a natural immunity. Other children giving a history of having had the disease before admission, or having had an attack of pertussis while in the institution, were grouped as those possessing an acquired immunity.
To possess a method whereby it would be possible to designate a child as having a natural or acquired immunity, and to be able to diagnose pertussis