Persistence of seroprotection 10 years after primary hepatitis A vaccination in an unselected study population

Abstract

Hepatitis A vaccines have been demonstrated to be highly immunogenic. Mathematical models have predicted antibodies to persist for at least 20–25 years. Most of these studies have been conducted in young and healthy study populations. We aimed to evaluate long-term immunity 10 years following complete primary immunization according to a 3-dose schedule (Havrix™ 720 El.U at months 0, 1, 6–12) in an adult and unselected study population. In total, 999 (98.3%) of 1016 vaccinees (mean age 54.7 ± S.D. 13.0), tested 10 years after primary vaccination, still had protective antibody levels (≥10 mIU/ml) as measured by ELISA. An anti-HAV titer cut off level of 11,400 mIU/ml was calculated to differentiate between vaccine-induced and infection-induced titer levels. The vaccine-induced geometric mean titer (GMT) was 406.1 mIU/ml (95% CI: 369.2–446.7 mIU/ml), showing an age-related trend, the 10-years seroprotection rate (SPR) was 97.9%. Females exhibited significantly higher GMTs than male vaccinees ( p < 0.001). The only parameter predicting a titer below 10 mIU/ml 10 years after vaccination was the body mass index ( p = 0.001). This study confirms that protection following primary hepatitis A vaccination persists for more than 10 years.