Administration of human normal
immunoglobulin (HNIG) post-exposure has been routinely used in Slovakia for outbreak control of
hepatitis A, but requires deep
intramuscular injection, provides only short-lived protection and is a human blood product. The protective effect of post-exposure administration of an inactivated
hepatitis A vaccine was evaluated during 10 outbreaks in Slovakia. Direct contacts of confirmed
hepatitis A cases received either: a single dose of
hepatitis A vaccine (n = 2171) or
immunoglobulin (HNIG, n = 3837). In the HNIG group the number of
hepatitis A confirmed cases dropped within the first 7 weeks, however the decrease was not as rapid or as marked as that observed in the vaccinated group where the number of
hepatitis A cases dropped within the first 4 weeks after vaccination. Among contacts, 67 cases of
hepatitis A were detected during the maximum incubation period of 45 days: 16 cases (0.7%) in the
vaccine group and 51 cases (1.3%) in the HNIG group (p < 0.05). After two and three years respectively, 50 and 39 volunteers who had previously received one dose of
hepatitis A vaccine received a booster dose and
anti-HAV antibodies were measured. Differences in
anti-HAV antibody GMCs before and after the booster were statistically significant. The longer time interval (3 years instead of 2) between primary vaccination and booster administration did not seem to impact the magnitude of the booster response. The results of this study show that active post-exposure immunisation with only one dose of
inactivated vaccine confers high and long-term protection and effectively controls viral
hepatitis A outbreaks.