Evaluation of recent pre-booster studies on hepatitis B vaccine effectiveness across WHO regions with HBV prevalence above 1% in the general population up to 60 years of age: a systematic review.

Hepatitis B vaccination has substantially reduced the global burden of HBV infection. However, the long-term vaccine effectiveness (VE) and the need for booster doses are still uncertain, especially in some age groups living in meso- and hyperendemic regions. WHO has therefore emphasized the need for further studies to identify subgroups requiring booster doses to ensure sufficient levels of protection against HBV infection. Accordingly, in the present review, we evaluate VE and the need for booster doses among healthy urban populations aged up to 60 years in the WHO regions where the HBV prevalence exceeds 1%. This systematic review included studies reporting VE stratified by age that expressed estimates as odds ratios, risk ratios, or absolute risk. Of the 2,421 studies identified in PubMed, Web of Science, and Scopus, 11 met the inclusion criteria. There were significant age-related trends in VE. Among the 20- to 59-year-olds, especially the 20–39 age group, the effectiveness was the lowest in the Eastern Mediterranean Region, namely Tunisia and Iran. In China, the highest breakthrough infection rates were reported in the 18–29 age group, highlighting the significance of considering booster doses for enhanced protection in this population. The highest-risk ages in Vietnam were found to be 33.7, 53.8, and 24.9 years. In Africa, although the effectiveness was high among those who had received complete vaccine dosages, it declined among those aged 30–59 years with increasing age. Increased abnormal ALT rates with advancing age, a predictor of chronic HBV infection, also highlighted the need for additional booster immunizations in Taiwan and Gambia. The results indicate waning vaccine effectiveness, particularly in individuals 20–59 years old in meso- to hyper-endemic regions. These findings strongly support revisiting the vaccination schedules with consideration for targeted booster doses to maintain immunity for a longer period. This review also highlights the fact that the assessment of vaccine effectiveness and its side effects in various age and geographical groups is incomplete.