Hepatitis A Virus ¨C Reduce Infections

Estimated^* new hepatitis A virus infections and annual targets for the United States by year

Source: CDC, National Notifiable Diseases Surveillance System1.

* The number of estimated viral hepatitis infections was determined by multiplying the number of reported cases by a factor that adjusted for underascertainment and underreporting.12

Summary of findings

The number of estimated new hepatitis A virus (HAV) infections increased annually beginning in 2015, peaked in 2019, and sharply decreased in 2020. This downward trend continued through 2023, reaching 3,300 estimated infections. This exceeds the annual target of 4,000 estimated infections and represents a 51% reduction from the 2017 baseline target. The continued decline in reported cases of hepatitis A in 2023 follows a period of several years of increasing numbers that peaked in 2019 due to widespread and prolonged hepatitis A outbreaks associated with person-to-person transmission, primarily occurring among persons who use drugs and those experiencing homelessness. These outbreaks highlight the importance of vaccinating persons at increased risk for HAV infection to prevent future outbreaks.

Further reduction can best be achieved by:

• Analyzing available data and other strategic information to describe populations at higher risk of infection and detect gaps in vaccination coverage.
• Building capacity within jurisdictions to collect and analyze surveillance data to identify where HAV infection is occurring, understand transmission networks, and enhance what is learned from outbreak investigations.
• Disseminating and implementing updated CDC recommendations for hepatitis A vaccination (including post-exposure prophylaxis) to reach medically underserved populations.3
• Promoting evidence-based strategies to increase vaccination as recommended by the and described in
• Strengthening state and local health departments' outbreak detection and response.

Technical notes

Data sources: CDC, National Notifiable Diseases Surveillance System (NNDSS)

Numerator: Number of estimated HAV infections

Denominator: Not applicable

Indicator notes: NNDSS is a nationwide collaboration that enables all levels of public health to share notifiable disease-related health information.1 Surveillance for viral hepatitis through NNDSS is based on case definitions developed and approved by the Council of State and Territorial Epidemiologists (CSTE) and CDC. . Estimated infections are based on laboratory-confirmed reports of hepatitis A cases; these estimates are presented in the 2023 Annual Surveillance Report1 along with their 95% confidence intervals to show the range of estimated infections accounting for error. Hepatitis A is reportable in all jurisdictions. Health care providers, hospitals, and/or laboratories report cases to the local or state health department, and states voluntarily submit reports or notify CDC of newly diagnosed cases of hepatitis A that meet the CSTE/CDC surveillance case definition. To account for underascertainment and underreporting, the number of reported cases is multiplied by 2.0 to estimate the number of HAV infections for a given year. The methods for developing the multiplication factor have been previously described and used by CDC to estimate the number of annual infections.12

Goal setting: The 2025 goal of 4,000 estimated infections is consistent with CDC’s Division of Viral Hepatitis 2025 Strategic Plan and the . Annual targets assume a constant (linear) rate of change from the observed baseline (2017 data year) to the 2025 goal (2023 data year).

Limitations: The number of estimated infections is based on a simple, probabilistic model for estimating the proportion of patients who were symptomatic, received testing, and were reported to health officials in each year.2 This constant multiplier might not account for variations over time in underreporting and underascertainment due to changes in public and provider awareness, laboratory and diagnostic techniques, and the case definition for the condition.