Hepatitis A Virus – 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 underreporting12.

Summary of findings

After annual increases beginning in 2015, the number of estimated hepatitis A virus (HAV) infections began to decrease in 2020. The year 2022 marks the third year the number of HAV infections has decreased. The 4,500 estimated infections in 2022 were a 32% reduction from the 2017 baseline and slightly higher than the 2022 target of 4,450 estimated infections. Because the COVID-19 pandemic caused disruptions in access to medical care, testing, and routine viral hepatitis public health activities, the 2020–2022 data should be interpreted with caution. The incidence of hepatitis A is subject to variation from year to year, in large part due to hepatitis A outbreaks. Since late 2016, there have been widespread outbreaks of hepatitis A across the United States, spread through person-to-person contact primarily among persons reporting drug use or homelessness. These community outbreaks have been prolonged and difficult to control in many states, highlighting the importance of administering hepatitis A vaccine in populations that are at increased risk for infection. Food-related outbreaks have occurred among persons in several states and were associated with imported pomegranate seeds in 2013, imported frozen strawberries and raw scallops in 2016, and fresh blackberries in 2019. These accounted for far fewer cases, occurred in fewer states, and had much shorter durations than the ongoing outbreaks driven by person-to-person transmission.

This reduction can best be achieved by:

• Disseminating and implementing updated CDC recommendations for hepatitis A vaccination (including postexposure prophylaxis) to reach medically underserved populations.3
• Strengthening state and local health departments' outbreak detection and response.
• Promoting evidence-based strategies to increase vaccination as recommended by the Community Preventive Services Task Force and described in Strategies for Successful Vaccination Among Two Medically Underserved Populations: Lessons Learned From Hepatitis A Outbreaks – PubMed (nih.gov).
• Analyzing available data and other strategic information to describe populations at higher risk of infection and detect gaps in vaccination coverage.
• Continuing to promote routine childhood vaccination schedules and vaccination of adults at increased risk for hepatitis A according to Advisory Committee on Immunization Practices Vaccine Recommendations and Guidelines.

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 information1. 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. Reported cases of hepatitis A are required to meet specific clinical and laboratory criteria. Estimated infections are based on laboratory-confirmed reports of hepatitis A cases; these estimates are presented in the 2022 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 under ascertainment and underreporting, the number of reported cases is multiplied by 2.0. 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 US Department of Health and Human Services' 2021–2025 Viral Hepatitis National Strategic Plan. 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 under ascertainment due to changes in public and provider awareness, laboratory and diagnostic techniques, and the case definition for the condition.