Abstract
The aim of this study was to analyse the impact of the introduction of universal adolescent HBV vaccination on the incidence of acute hepatitis B virus (HBV) infections. Acute HBV cases reported to the Spanish National Epidemiological Surveillance Network between 2005 and 2021 were included. For regions starting adolescent vaccination in 1991-1993 and in 1994-1996, HBV incidence rates were compared by calculating the incidence rate ratio (IRR) and 95% confidence interval (CI). We also analysed the 2017 Spanish national seroprevalence survey data. The overall acute HBV incidence per 100,000 persons was 1.54 in 2005 and 0.64 in 2021 (p < 0.001). The incidence in 2014-2021 was lower for regions that started adolescent vaccination in 1991-1993 rather than in 1994-1996 (IRR 0.76; 95% CI 0.72-0.83; p < 0.001). In the 20-29 age group, incidence in regions that started adolescent vaccination in 1991-1993 was also lower (IRR 0.87; 95% CI 0.77-0.98; p = 0.02 in 2005-2013 and IRR 0.71; 95% CI 0.56-0·90; p < 0.001 in 2014-2021). Anti-HBc prevalence in the 35-39 age group was lower in the regions that started vaccination earlier, although the difference was not statistically significant (p = 0.09). Acute HBV incidence decreased more in the young adult population in regions that began adolescent vaccination earlier. Maintaining high universal vaccination coverage in the first year of life and in at-risk groups is necessary to achieve HBV elimination by 2030.