Impact and effectiveness of a mass hepatitis A vaccination programme of preadolescents seven years after introduction

Aim: To investigate the impact of a mass hepatitis A vaccination programme in preadolescents seven years after introduction in terms of its effectiveness and the prevented fraction. Setting: The age distribution of notified cases and incidence rates in Catalonia (Spain) in the periods before (1992-1998) and after (1999-2005) introduction of the vaccination programme were compared. Main results: The incidence rates in the whole population were 5.51 per 100,000 person-years in the 1992-1998 period and 2.98 in the 1999-2005 period. The rate reduction in the 10-19 years age group was 72.43% and was more than 45% in the 5-9 years and 20-29 years age groups. The effectiveness of the vaccination programme was 99.04 (95% CI: 93.11-99.88) and the prevented fraction in the 12-19 years age group was 90.13% (95% CI: 84.47-90.89). Conclusions: The universal vaccination programme of preadolescents has had an important impact on hepatitis A in Catalonia, not only in vaccinated cohorts but also in non-vaccinated age groups due to a herd immunity effect.