AbstractBackground and objectives:
Antibody persistence and immune memory against hepatitis A (HAV) in adults in a low endemicity country, 15 y after immunization with two doses of HAV vaccine has been demonstrated. This communication provides additional information on antibody persistence up to Year 17 from two of the longest follow-up studies [NCT00289757/NCT00291876].Methods:
In two double-blind primary studies, healthy adults aged 17–40 y and 21–40 y, respectively received two doses of the HAV vaccine following a 0,6 mo or 0,12 mo schedule. Anti-HAV antibody concentrations were measured using an enzyme-linked immunoassay (cut-off: 15 mIU/ml) at Year 16 and Year 17. Subjects who became seronegative (anti-HAV < 15 mIU/ml) since previous reporting were offered a challenge dose, with anti-HAV antibody concentration measurements at Day 14 and Day 30 thereafter.Results:
At Year 17, 100% and 96.7% of subjects remained seropositive for anti-HAV antibodies following the 0, 6 mo and 0, 12 mo regimens, respectively (GMCs: 278 mIU/ml and 369 mIU/ml). One subject who became seronegative at Year 16 received a HAV challenge dose within the next 12 mo and mounted an anamnestic response. The challenge dose was well-tolerated.Conclusions:
Both HAV immunization regimens (0,6 mo and 0,12 mo) induced persistence of vaccine-induced antibodies against HAV for at least 17 y after primary vaccination.