Diphtheria, tetanus, pertussis: antibody detection in New Zealand.

Enzyme-linked immunosorbent assay (ELISA) tests were developed to detect IgG antibodies to diphtheria, tetanus, and pertussis in a healthy New Zealand population. Sera from 551 healthy persons aged 6-65 years from different areas in New Zealand were tested. Immunity to diphtheria decreased steadily from 97.1% in the 6-9 age group to 47.6% in the 60-65 age group. Immunity to tetanus varied from 88.6% in the 6-9 age group to 83.3% in the 20-29 age group, whence the level decreased with age to 57.1% in the 60-65 age group. In the teenage and adult groups more than 87.6% have antibodies to pertussis while in the 60-65 group it was 66.7%. There was great variation in the level of measurable antibody to pertussis in all age groups.