Population immunity to hepatitis B virus and infection marker seroprevalence in Belgrade, Serbia.

UNLABELLED: Despite global progress in hepatitis B (HB) control, assessing herd immunity and the hidden burden of infection remains critical.

AIM: This study aimed to comprehensively evaluate immunity to hepatitis B virus and HB marker prevalence in the Belgradian population (Serbia) based on infection/vaccination status and socio-demographic characteristics.

MATERIALS AND

METHODS

A cross-sectional study was conducted in Belgrade in May 2024, involving 2,533 individuals. Serological markers (HBsAg, anti-HBc, anti-HBs) were evaluated using ELISA. Statistical analysis included the calculation of 95% confidence intervals, the χ2 test, and Spearman's correlation analysis.

RESULTS

The overall HBsAg prevalence was 1.0% (25/2,533), classifying Serbia as a low-endemicity region. The seroprevalence of anti-HBc and anti-HBs was 8.7% (220/2,533) and 21.6% (547/2,533), respectively. A clear age-dependent trend was observed. Markers of infection (HBsAg, anti-HBc) increased significantly with age (rs = 0.823 and rs = 0.898, respectively) among adults, peaking in the 70+ years group for anti-HBc (22.2%, 42/189). In contrast, protective anti-HBs antibodies showed a negative correlation with age (rs = -0.75), being most prevalent in children and young adults (76.9%, 10/13, in the group 1-5 years). Vaccination coverage also showed a strong negative correlation with age (rs = -0.95), declining from 82.3% (93/113) among individuals under 18 to 4.6% (16/345) among retirees. These correlations clearly illustrate differing epidemiological profiles. They range from high natural viral circulation among older, unvaccinated cohorts to effective infection control through vaccine-induced immunity in the younger generation. A low level of population awareness was identified: only 1.1% (28/2,533) of respondents reported a history of HBV, whereas serological data indicated that 8.7% (220/2,533) of the population had markers of viral exposure.

CONCLUSION

The study confirms the success of the universal child vaccination program in Serbia, which has led to the formation of a protected younger generation. However, a significant susceptible stratum persists among the adult population, alongside a high rate of undiagnosed infections, particularly in the older adults. These findings underscore the necessity of implementing targeted adult screening programs and optimizing vaccination strategies to achieve HB elimination.