During the past several years a number of unrelated studies and investigations have amassed material which when put together forms an interesting picture of diphtheria immunity and factors affecting it in a community. Diphtheria antitoxin is at present the only readily measurable immune substance and its exact relation to a person's resistance to diphtheria is by no means fully comprehended. However, both the Schick test and the diphtheria antitoxin determinations on human serum provide methods for studying immunity to diphtheria in a population that should be instructive.
In anthropometric studies attempts have been made to correlate the susceptibility of persons with distinct body types to certain diseases. If variability in immunity to a given disease occurs and if that immunity is measurable, a frequency distribution curve for immunity in a cross section of the population comparable to the frequency curves for other characteristics should be possible. Variations in immunity were
THELANDER HE. DIPHTHERIA IMMUNITY AND FREQUENCY DISTRIBUTION CURVES FOR ANTITOXIN. Am J Dis Child. 1940;59(2):342–352. doi:10.1001/archpedi.1940.01990130125009