Changes in Hepatitis A seroprevalence over 11 years and the impact of the National Vaccination Program in Bursa, Türkiye

Hepatitis A virus (HAV) infection remains a significant cause of acute viral hepatitis worldwide. Türkiye has transitioned from historically high endemicity to an intermediate-endemic setting, and the national childhood vaccination program introduced in 2012 has further influenced epidemiological patterns. We retrospectively analyzed 28,067 patients tested for anti-HAV IgG and IgM at Bursa Uludağ University Hospital between 2014 and 2024, a large tertiary-care referral center. Serological assays were performed using chemiluminescent microparticle immunoassays. Results were categorized by age, sex, and year of testing. IgM-positive cases were further evaluated for clinical and laboratory correlation. The mean age was 36.1 years, and 51.7% were male. Overall, anti-HAV IgG seropositivity was 68.97%, ranging from 31.82% in the 21–25-year age group to 99.66% among those ≥ 60 years. Children born in 2012 or later (vaccine-eligible cohort) exhibited an anti-HAV IgG seropositivity rate of 93.3%, with no anti-HAV IgM positivity. Anti-HAV IgM was detected in 0.26% (72/28,067); however, only 19 cases (26.4%) fulfilled the criteria for acute hepatitis A, and 42% occurred in August–September. Remaining IgM reactivity was mostly asymptomatic/unlikely acute HAV or possible false positivity, frequently accompanied by HBV/HCV infection, EBV infection, autoimmune disease, or malignancy. Cut-off indices were significantly higher in confirmed acute cases (p < 0.001). Bursa, Türkiye, continues to exhibit intermediate HAV endemicity. The childhood vaccination program supports its effectiveness by demonstrating high seropositivity and the absence of IgM positivity in the vaccine-eligible cohort; however, false-positive IgM reactivity underscores the importance of clinical and laboratory confirmation.