A study published yesterday in JAMA Internal Medicine reveals low serologic immunity to hepatitis A virus (HAV) and hepatitis B virus (HBV) among US adults, including those at high risk for infection.

Using data from the National Health and Nutrition Examination Survey from January 2017 to August 2023, researchers from the University of Minnesota and the Minneapolis Veterans Affairs Health Care System evaluated HAV and HBV serologic test results from 13,514 adults aged 20 and older for the presence of antibodies from previous infection or vaccination.

“Universal birth-dose HBV vaccination, adopted in the US in 1991, was associated with a 95% reduction in infant HBV infections, preventing approximately 90 000 deaths,” they wrote.

“However, in December 2025, the Centers for Disease Control and Prevention (CDC) and the Advisory Committee on Immunization Practices (ACIP) updated guidelines to recommend individual-based decision-making for infants of mothers without HBV infection, replacing universal birth-dose vaccination,” they added.

The average participant age was 48.7 years, and 51.8% were women. In total, 39.5% of adults were serologically immune to HAV, 27.1% had serologic immunity to HBV, and 25.2% showed vaccine-derived immunity.

Safe and effective vaccines prevent HAV and HBV infections, and serologic immunity protects high-risk populations from severe outcomes.

HAV immunity was tied to younger age (adjusted odds ratio [aOR], 0.51); lower educational attainment (aOR, 0.32); and Black (aOR, 1.67), Mexican-American (aOR, 4.22), other Hispanic (aOR, 2.01), Asian (aOR, 3.03), and multiracial or other race and ethnicity (aOR, 1.36); as well as birth outside the United States (aOR, 4.54) and awareness of liver disease (OR, 1.65). Obesity was linked to lower odds of being immune to HAV (aOR, 0.83). 

Vaccine-derived HBV immunity was associated with younger age (aOR, 0.18), female sex (aOR, 1.36), Asian (aOR, 1.47) and Black (aOR, 1.15) race, and higher educational attainment (aOR, 3.29). 

Among all adults, 66.9% were categorized as high risk. In these subgroups, HAV immunity ranged from 26.7% for metabolic dysfunction–linked alcohol-related liver disease to 63.7% for chronic HBV infection, while vaccine-derived HBV immunity ranged from 14.0% for chronic kidney disease to 38.6% for pregnancy.

The low rates of immunity, which previous studies have also found, may be explained by the aging of naturally immune cohorts who had HAV in childhood, when infection was more common; suboptimal HAV vaccination coverage among younger adults; and COVID-19 pandemic disruptions to preventive healthcare access, the authors said. 

The findings establish a baseline for evaluating the CDC policy change from universal birth-dose HBV vaccination to shared clinical decision-making for low-risk infants, they added.

“Safe and effective vaccines prevent HAV and HBV infections, and serologic immunity protects high-risk populations from severe outcomes,” the researchers wrote. “In light of growing public concern regarding vaccine safety and benefit and recent changes in ACIP HBV vaccination policy, maintaining evidence-based vaccination strategies remains essential.” 

In an editorial published in the same journal, Melinda Wang, MD, MHS, of the University of California San Francisco, and colleagues, note that infants are particularly vulnerable to hepatitis, with roughly 90% of those exposed to HBV developing chronic disease, compared with 30% of children aged 1 to 5 years and 5% of adults.

Although chronic hepatitis B can be treated, it is both incurable and may be associated with cirrhosis, liver failure, and hepatocellular carcinoma.

“Although chronic hepatitis B can be treated, it is both incurable and may be associated with cirrhosis, liver failure, and hepatocellular carcinoma,” they wrote.

While the effects of the 2025 hepatitis vaccine policy change aren’t yet clear, it is likely to lead to increased rates of hepatitis, they added.

Thus, the findings, the researchers concluded, “should spur active efforts by clinicians to boost vaccination efforts and prevent serious long-term sequelae for these groups.”