Effectiveness of hepatitis A vaccination as post-exposure prophylaxis.

Hepatitis A (HA) has been a vaccine-preventable disease since 1995. In Catalonia, a universal combined hepatitis A+B vaccination program of preadolescents was initiated at the end of 1998. However, outbreaks are reported each year and post-exposure prophylaxis (PEP) with hepatitis A virus (HAV) vaccine or immunoglobulin (IG) is recommended to avoid cases. The aim of this study was to assess the effectiveness of HAV vaccine and IG in preventing hepatitis A cases in susceptible exposed people. A retrospective cohort study of contacts of HA cases involved in outbreaks reported in Catalonia between January 2006 and December 2012 was made. The rate ratios and 95% confidence intervals (CI) of HA in susceptible contacts receiving HAV or IG versus those without PEP were calculated. There were 3550 exposed persons in the outbreaks studied: 2381 received one dose of HAV vaccine (Hepatitis A or hepatitis A+B), 190 received IG, and 611 received no PEP. 368 exposed subjects received one dose of HAV vaccine and IG simultaneously and were excluded from the study. The effectiveness of PEP was 97.6% (95% CI 96.2-98.6) for HAV vaccine and 98.3% (95% CI 91.3-99.9) for IG; the differences were not statistically significant (p = 0.36). The elevated effectiveness of HAV vaccination for PEP in HA outbreaks, similar to that of IG, and the long-term protection of active immunization, supports the preferential use of vaccination to avoid secondary cases.