Global, Regional, and National Time Trends in Incidence for Hepatitis A, 1990-2021: A Systematic Analysis for the Global Burden of Disease 2021 Study.

Hepatitis A is the most common form of acute viral hepatitis, and its control is critical to achieving the 2030 viral hepatitis elimination target. We conducted a comprehensive assessment of hepatitis A incidence across 204 countries and regions from 1990 to 2021. Annual incident cases and age-standardized incidence rates (ASIR) of hepatitis A were obtained from the Global Burden of Disease (GBD) study 2021. Joinpoint regression analysis evaluated long-term trends in ASIR, while Age-Period-Cohort (APC) analysis assessed the independent effects of age, period, and cohort. Decomposition analysis determined the drivers behind temporal changes in disease incidence. The Slope Index of Inequality (SII) and Concentration Index (CI) were employed to quantify cross-national inequalities in incidence. From 1990 to 2021, global hepatitis A cases declined by 7.25%, with age-standardized incidence rates (ASIR) demonstrating a universal downward trend. The most substantial ASIR reductions occurred in low-middle socio-demographic index (SDI) quintiles, whereas low-SDI quintiles showed paradoxical ASIR declines (AAPC: -1.56 95% CI: -1.71 to -1.40) alongside a 39.44% (95%UI: 28.04 to 50.48) case surge. Cases remained concentrated in children under 5. The age-period-cohort analysis confirmed highest risk in young children, with period and cohort risks declining over time. Decomposition analysis identified population growth as the primary driver of case increases. Health inequality analysis showed persistent absolute disparities despite relative improvements. Although global hepatitis A incidence has declined over three decades, trends are highly heterogeneous and significant inequalities persist. Achieving equitable burden reduction requires differentiated strategies and enhanced international collaboration, particularly for low-resource settings.