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.

Global epidemiology of hepatitis B virus infection: new estimates of age-specific HBsAg seroprevalence and endemicity.

OBJECTIVE: Chronic hepatitis B virus infection is one of the most serious infections and a major risk factor for deaths from cirrhosis and liver cancer. We estimate age-, sex- and region-specific prevalence of chronic HBV infection and calculate the absolute number of persons being chronically infected. METHODS: A systematic review of the literature for studies reporting HBV infection was conducted and worldwide HBsAg seroprevalence data was collected over a 27-year period (1980-2007). Based on observed data, age-specific prevalence and endemicity were estimated on a global level and for all world regions for 1990 and 2005 using an empirical Bayesian hierarchical model. FINDINGS: From 1990 to 2005, the prevalence of chronic HBV infection decreased in most regions. This was particularly evident in Central sub-Saharan Africa, Tropical and Central Latin America, South East Asia and Central Europe. Despite this decrease in prevalence, the absolute number of HBsAg positive persons increased from 223 million in 1990 to 240 million in 2005. Age-specific prevalence varied by geographical region with highest endemicity levels in sub-Saharan Africa and prevalence below 2% in regions such as Tropical and Central Latin America, North America and Western Europe. Asian regions showed distinct prevalence patterns with lower intermediate prevalence in South Asia, but up to 8.6% HBsAg prevalence in East Asia. Strong declines were seen in South East Asian children. CONCLUSION: Declines in HBV infection prevalence may be related to expanded immunization. The increasing overall number of individuals being chronically infected with HBV, and the widespread global differences in HBV prevalence call for targeted approaches to tackle HBV-related mortality and morbidity. HBV infection prevalence data are needed at country and sub-national level to estimate disease burden and guide health and vaccine policy.