Hepatitis A infection in New Zealand children.

Antibody to hepatitis A virus (anti HAV), a marker of past infection, was assayed in 2000 sera collected as part of a national survey in 1978-79. The sera were obtained from children and young people aged 0-21 years, resident in all health districts of New Zealand. Anti HAV was detected in 307 sera, giving an overall prevalence of 15.4%. Prevalence increased steadily throughout childhood but more slowly during adolescence. There was no sex differential, the age-standardised rate/100 being 15.5 (95% confidence interval 13.2, 17.8) for males and 16.6 (14.4, 18.9) for females. However, the age-standardised rate for Maoris was 39.5 (33.2, 45.8) compared to 16.1 (12.8, 19.4) for Europeans, giving a risk ratio of 2.1. In addition, a marked north-south gradient in prevalence was demonstrated: the rate for children in the northern half of the North Island, when standardised for age and ethnicity, was 19.8 (16.8, 22.7) compared to 5.2 (3.2, 7.1) for South Island children, giving a risk ratio of 3.8. The higher prevalence of hepatitis A infection in Maori and northern North Island children mirrors our previously reported findings regarding markers of hepatitis B infection in this serum collection.