Hepatitis A Chronic Immunity: A Population-Based Seroprevalence Study in Fars Province, Southern Iran

Background: Hepatitis A virus (HAV), the most common cause of acute viral hepatitis, afflicts millions of people and causes the loss of thousands of lives annually. Objectives: This study aimed to detect the seroprevalence of anti-HAV IgG in Fars province, Iran. Methods: This cross-sectional study was conducted using multi-stage cluster random sampling from 12 cities and 24 villages. All age groups, excluding infants (≤ 1-year-old), were included in this study. A valid checklist consisting of demographic and sanitation items and questions about the transmission routes of HAV were filled out for each individual. In the case of children, interviews were performed with one of the parents. Furthermore, anti-HAV IgG was detected by enzyme-linked immunosorbent assay (Dia.pro kits, Italy) on 3 cc of the blood sample of each participant. Data were analyzed using univariate and multivariate (binary logistic regression) tests by SPSS. We applied both World Health Organization (WHO) and age at mid-point of population immunity (AMPI) protocols for HAV endemicity classification. In addition, the geographical variation of hepatitis A chronic immunity was analyzed by the Bayesian spatial model. OpenBUGS program was used to estimate parameters, and ArcGIS was used to display the results on a map. Results: A total of 547 participants with an age range of 1 - 82 years, mean age of 33.07 ± 15.1 years, and female to male ratio of 1.1 were studied. Overall, 380 (69.5%) individuals had anti-HAV IgG, and 124 of 282 (44%) adults ≤ 30 years old had HAV immunity. AMPI was 25 years old. Being married (OR = 10.7), non-Fars ethnicity (OR = 2.8), knowledgeable about HAV (OR = 2.2), and employed (OR = 1.7) were the strongest determinants of anti-HAV seropositivity. Southern cities of Fars province, which have a hot climate, had the highest prevalence of HAV immunity. Conclusions: Fars province is a very low and intermediate HAV endemic area based on WHO and AMPI protocols, respectively. High-risk groups, such as patients with chronic liver diseases or coagulopathy, travelers to highly-endemic areas, intravenous drug abusers, and homosexuals, should be given priority in the HAV vaccination program. However, the strategy of HAV vaccination should be tailored to subsequent cost-effectiveness studies and national HAV vaccination strategy.