Decadal changes in IgG seroprevalence of hepatitis A and E virus in Urban Vellore, India: Persistent Endemicity or Epidemiological Shift?

Hepatitis A virus (HAV) and hepatitis E virus (HEV) are major causes of acute viral hepatitis in low- and middle-income countries (LMIC) and are closely linked to sanitation, hygiene, and socio-economic conditions. Rapid urbanisation and improvements in water and sanitation infrastructure may alter exposure patterns, leading to epidemiological transition and changing population immunity. We conducted a two cross-sectional seroprevalence study on biobanked samples in urban wards of Vellore, South India, in 2013 and 2022. Serum samples from 600 participants in 2013 and 558 participants in 2022, aged 1–40 years, were tested for HAV and HEV IgG antibodies. Seroprevalence estimates were stratified by age, gender, and cluster. Differences in seropositivity between survey years were assessed using proportion tests or Fisher’s exact tests for both viruses and age-stratified susceptibility patterns and Re (effective reproduction number) were assessed for HAV using contact matrix and mixture modelling. HAV IgG seroprevalence was consistently high across all age groups in both surveys, exceeding 80% among children aged 1–5 years and reaching 100% among individuals aged ≥ 16 years in 2013 and 2022. No statistically significant differences in HAV seroprevalence were observed between survey years. In contrast, HEV IgG seroprevalence was low among children and adolescents in both surveys and increased with age. Among adults aged 26–40 years, HEV seroprevalence increased from 18% (95% CI: 12–27) in 2013 to 24% (95% CI: 16–32) in 2022, although this change was not statistically significant. No significant gender-based differences were observed for either virus. Cluster-wise analysis demonstrated uniformly high HAV seroprevalence, whereas HEV seroprevalence was low and heterogeneous across clusters. Mixture modelling of the HAV data showed the Re of < 1 across both the sero-surveys reflecting no change in the secondary transmission despite increased susceptibility among older age groups. A decade apart, population immunity to HAV remained high in this urban setting, while HEV exposure remained limited and age dependent. These findings support continued investment in water, sanitation, and hygiene interventions and highlight the need for targeted HEV surveillance, while informing age-specific considerations for HAV vaccination policy in urban India undergoing transition. Not applicable.