SINGLE DOSE-INACTIVATED HEPATITIS-A VACCINATION SCHEDULE FOR SUSCEPTIBLE YOUNGSTERS

Objective: To investigate the feasibility of a single-dose primary hep atitis A vaccination for young travelers. Methods: One hundred and nin eteen susceptible youngsters, 9-18 yr old, received a dose of 720 ELIS A units of the inactivated hepatitis A vaccine at month 0, and then a booster at month 6. Results: Antibodies to hepatitis A virus (anti-HAV ) seroconversion (greater than or equal to 20 mIU/ml) in these vaccine es was 91% (106/117) on day 15, and reached 99% (118/119) 1 month afte r the single-dose vaccination. At month 6 before the booster, 97% (110 /113) of the vaccinees still had detectable anti-HAV. All vaccinees (1 13/113) had measurable titers of anti-HAV 1 month after booster vaccin ation, and were still seropositive (68/68) at month 12. The anti-HAV r esponse was found to be slower in vaccinees positive for hepatitis B s urface antigen (11/16, 68.8%), compared with noncarrier vaccinees (95/ 101, 94.1%; p < 0.01) 15 days after the priming dose. After initial va ccination, the geometric mean titers of anti-HAV among vaccine respond ers were 220, 255, 117, 3308, and 1094 mIU/ml at day 15 and months 1, 6, 7, and 12, respectively. Conclusion: These results suggest that a s ingle dose of hepatitis A vaccine could be a good alternative to immun e serum globulin administration for immunoprophylaxis in young healthy travelers.