SIGNIFICANCE OF IMMUNITY TESTS IN. EPIDEMIOLOGY AS ILLUSTRATED IN YELLOW FEVER

Abstract

Immunity tests are taking an important place in epidemiologic studies of several diseases of man. In diphtheria, scarlet fever and tuberculosis skin tests are commonly used. In poliomyelitis and yellow fever the serum is tested in animals, in the former by a neutralization test and in the latter by a protection test. If a result indicating immunity is obtained by any of these procedures, it is assumed that the person tested has previously been infected with the corresponding causative agent. Such evidence of a preceding immunizing infection is so frequent in persons who give no history of an attack of the disease under investigation that a high prevalence of unrecognized and subclinical cases is commonly assumed. Another possible explanation would be that the immunity tests are not so specific or so reliable as has been believed. The specificity of immunity reactions, particularly the Schick test in diphtheria, has been questioned