The 1985 national immunisation survey: diphtheria, tetanus, and pertussis (whooping cough)

In April 1985 a national immunisation survey was conducted in which sera were collected from almost 3000 randomly selected children throughout New Zealand. The sera collected were from about 1000 new school entrants (mean age 5 years), 1000 standard 3 students (mean age 10 years), and 1000 form 4 students (mean age 15 years). The sera were tested for diphtheria and tetanus immunity and antibody to pertussis by enzyme-linked immunosorbent assay (ELISA) tests. The percentage of those immune to diphtheria decreased with age from 73.1% in the 5 year olds to 53.7% in the 15 year olds. The percentage of those immune to tetanus decreased with age from 66.9% in the 5 year olds to 54.6% in the 10 year olds but then increased to 64.0% in the 15 year olds. While more than 71.0% of the 10 and 15 year olds had measurable antibody to pertussis, only a low 54.4% of the 5 year olds did. The proportion immune to diphtheria and tetanus in both Maoris and Europeans was approximately similar in all three age groups. More Maoris (78.9%) than Europeans (66.1%) had antibody to pertussis. When the data had been standardised for age and ethnic group the percentage with antibody to pertussis and immunity to diphtheria was highest in the southern region, while for tetanus immunity the percentage immune was highest in the northern and southern regions. We conclude that a sizeable pool of new school entrants (mean age 5 years) without antibody to pertussis is accumulating at a time when pertussis still persists.(ABSTRACT TRUNCATED AT 250 WORDS)