This study is thought-provoking and casts some doubt on our criteria for the measurement of immunity. It is a thoroughly performed report, attempting to explain why diphtheria has not been completely eradicated in certain population groups of Great Britain that have been immunized.
The following factors were examined: 1. There is no correlation between circulating antitoxin and attack rate. 2. Mitis, intermedius, and gravis types produce toxin which basically is identical. 3. The mortality rate in previously immunized groups is nil. 4. Some persons respond poorly to stimuli (toxoid). 5. Approximately 70% of persons in an epidemic area have to be immune before an epidemic can be brought under control.
This report should be valuable to those interested in the public health and pediatric aspects of the control of diphtheria.