Key result
An inactivated hepatitis A vaccine given at a 0-12 month schedule resulted in a 96.9% seroconversion rate at 4 weeks versus 100% for a 0-6 month schedule, with comparable booster responses.
Why the study?
Does an inactivated hepatitis A vaccine given at 0 and 12 months provide comparable immunogenicity to a 0 and 6 month schedule in adult volunteers?
RCT (n=96)
Open-label
randomized
No
Does an inactivated hepatitis A vaccine given at 0 and 12 months provide comparable immunogenicity to a 0 and 6 month schedule in adult volunteers?
A booster dose of inactivated hepatitis A vaccine can be effectively given at 12 months after primary immunization, providing comparable immunogenicity to a 6-month booster schedule.
Answers are grounded in this paper and cite their sources.
Enables flexible 0-12 month hepatitis A dosing in adults; extends RCT evidence for schedule adaptability.
BACKGROUND: Inactivated hepatitis A vaccines are licensed with a vaccination schedule based on two injections of vaccine given at least 6 months apart. METHODS: Two vaccination schedules for the inactivated hepatitis A vaccine, AvaximTM (Pasteur Mérieux Connaught, Lyon, France), were compared in a monocentric, randomized, open trial. Two doses of the vaccine were given at intervals of either 6 months (0-6 month group) or 12 months (0-12 month group) to 96 adult volunteers. Anti-hepatitis A virus (HAV) antibody titers were determined in a blind fashion using the modified RIA (mRIA) HAVABtrade mark assay. After excluding subjects with positive preimmunization anti-HAV titers and those with protocol deviations, both groups were still comparable by sex ratio and mean age. RESULTS: Four weeks (28 6 4 days) after the first dose, the seroconversion (SC) rate of initially HAV-seronegative subjects (antibody titer < 20 mIU/mL) was 100% in the 0-6 month group and 96. 9% in the 0-12 month group, with corresponding geometric mean titer (GMT) values (95% CI) of 369 mIU/mL (274-497 mIU/mL) and 445 mIU/mL (292-679 mIU/mL), respectively. After 6 months, SC was obtained in all subjects, and the corresponding GMT values were 349 mIU/mL and 359 mIU/mL in the 0-6 month group and the 0-12 month group, respectively. Four weeks after the booster dose given at 6 months, a 14.5-fold rise in GMT was observed. In the 0-12 month group, anti-HAV GMT values decreased by only 20% from 6 months to 12 months with a pre-booster GMT value of 286 mIU/mL at the 12-month evaluation. Four weeks after the booster given at 12 months, a 22. 5-fold rise in GMT was observed. Statistical analysis showed that the two vaccination schedules were comparable in their ability to boost antibody titers. Unsolicited reactions to vaccination were not different to those reported during earlier trials. Less than 12% of the vaccinees reported reactions after the first dose (11/93), or after the booster dose (11/92). CONCLUSIONS: This trial demonstrated antibody persistence is excellent for at least 12 months after one dose of this vaccine, and that a booster may be given at any time between 6 and 12 months after primary immunization.
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Vidor et al. (1998) conducted an RCT in Hepatitis A immunization (n=96). Inactivated hepatitis A vaccine (0-12 month schedule) vs. 0-6 month schedule was evaluated on Seroconversion rate 4 weeks after the first dose. An inactivated hepatitis A vaccine given at a 0-12 month schedule resulted in a 96.9% seroconversion rate at 4 weeks versus 100% for a 0-6 month schedule, with comparable booster responses.
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