Impact of neonatal hepatitis B vaccination programme on age-specific prevalence of hepatitis B infection in teenage mothers in Hong Kong.

We examined the impact of the neonatal hepatitis B immunization programme, first provided to all neonates born to mothers screened positive for hepatitis B surface antigen (HBsAg) in late 1983, on the age-specific prevalence of HBsAg carriage in teenage mothers managed in 1998–2008. HBsAg carriage was found in 2.5%, 2.7%, 8.8% and 8.0% of mothers aged ≤ 16, 17, 18, and 19 years, respectively (P=0.004), which was also correlated with advancing age (P=0.011). While neither difference nor correlation with age was found in mothers born before 1984, the prevalence of 1.2%, 1.5%, 7.1% and 8.3%, respectively, was significantly different among (P=0.008) and correlated with (P=0.002) age in mothers born 1984 onwards. Regression analysis indicated there was a significantly higher incidence of HBsAg carriage from age 17 onwards (adjusted odds ratio 2.55, 95% confidence interval 1.07–6.10, P=0.035), suggesting that the protective effect of the vaccine declined in late adolescence.