Seroprevalence of Hepatitis A in Oman Prior to National Vaccination.

Background: The hepatitis A virus (HAV) is a major cause of acute viral hepatitis and a significant global health concern. This study provides a pre-vaccination baseline for Oman, enabling longitudinal comparison with post-hepatitis A vaccination cohorts. This study aimed to determine the pre-vaccination seroprevalence of HAV antibodies (anti-HAV) in Oman and explore the associated demographic factors. Methods: A cross-sectional study was conducted from April 2014 to August 2015 among patients attending the medical outpatient clinic of the Medical City Hospital for Military and Security Services. Demographic data were collected via a structured questionnaire, and serum samples were tested for anti-HAV immunoglobulin IgG and IgM using enzyme-linked immunosorbent assays. Multivariate analysis was performed to identify the predictors of anti-HAV seroprevalence. Results: Among 1975 participants, 88.1% were positive for anti-HAV IgG. The mean age was 37.4 ± 16.1 years; however, those negative for anti-HAV IgG were considerably younger (mean age: 24.8 ± 15.7 years). Anti-HAV IgG seroprevalence was 37% in individuals aged ≤18 years and 91% in those >18 years (p < 0.001). The factors associated with seropositivity included older age (p < 0.001), consuming food prepared outside the home (p < 0.001), occupation (p < 0.001), and education level (p = 0.003). In the multivariable analysis, only age showed a strong independent association with serostatus: per 10-year increase, the aOR for anti-HAV IgG seropositivity was 2.87 (95% CI 2.25-3.63; p < 0.001). Conclusions: Our study estimates show high anti-HAV IgG seroprevalence and serve as a pre-vaccination baseline for evaluating the hepatitis A vaccination program in Oman over time. Given the lower natural exposure among younger cohorts, continued routine vaccination, scheduled serosurveys, and strengthened surveillance are required to identify emerging immunity gaps and prevent future HAV outbreaks.