Abstract
The diphtheria immunity status was determined with the passive haemagglutination technique in 503 sera of 10-90-year-old persons from Warsaw and Olsztyn Provinces. Donors of sera were students, teachers, pregnant women, employees of industry and medical service. The immunity was highest (90% of titers 0.1 IU/ml or higher) in persons below 20 years of age and in persons above 60 years of age (55%). Between these two groups, gaps in immunity exist, the proportion of those immune varying from 36-50% in the 20- 60-year-old groups. Since a large pool of susceptible persons creates an epidemic potential it was suggested that the adult type of tetanus-diphtheria toxoid (Td) should be introduced into the routine immunization schedule for high risk groups. These groups might include professional or age groups who are vulnerable to reintroduction of virulent Corynebacterium diphtheriae such as kindergarten and creches personnel, teachers, students, military service personnel and persons travelling to developing countries.