Single-dose administration of inactivated hepatitis A vaccination in the context of hepatitis A vaccine recommendations.

OBJECTIVES: Our objective was to identify evidence on the protection achieved by single-dose use of inactivated hepatitis A vaccines in order to evaluate the potential of a flexible booster administration in the form of a second dose.
METHODS: A search was conducted for evidence on single-dose administration of inactivated hepatitis A vaccine and its potential impacts on long-term seropositivity rates. The main pharmaceutical vaccine manufacturer federations and the corresponding authors of manuscripts were approached for additional epidemiologic data. Correspondence was also sent to the Argentinean Ministry of Health.
RESULTS: We identified 15 data sources reporting on protection achieved by a single dose of inactivated hepatitis A vaccine. The consistent finding was that the immune and memory response to the booster dose, or post-booster geometric mean titer, was independent of the time since initial vaccination. The impact of the booster on seroprotection was the same across sexes and age-groups. The longest time interval between initial and booster dose was 10.67 years, indicating that booster doses can be highly immunogenic for up to 10.67 years after primary vaccination.
CONCLUSIONS: Protective anti-hepatitis A virus antibody levels after a single dose of inactivated hepatitis A vaccine can persist for almost 11 years and increase or reappear after booster vaccination. Further research on the vaccine doses needed to achieve long-term protection against hepatitis A infection is required.