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Hepatitis B Vaccination Dramatically Lowers Prevalence among U.S. Children

Children and adolescents in the U.S. today have a very low likelihood of hepatitis B virus (HBV) infection thanks to widespread vaccination, according to an epidemiological study described in the March 1, 2011, Annals of Internal Medicine. Many adults remain vulnerable, however, underlining the importance of vaccination for at-risk groups.

The study sample consisted of 39,787 participants age 2 years and up who took part in the National Health and Nutrition Examination Survey (1999 to 2008), a representative, cross-sectional household survey. NHANES participants were interviewed about their health status and underwent physical exams, including blood tests. Being a household survey, it did not include military personnel, prisoners, homeless people, or people in nursing homes and other group care facilities.

Among people age 6 or older, chronic HBV infection was defined as detectable serum HBV surface antigen (HBsAg). Past exposure, or cleared infection, was determined by presence of serum antibodies against hepatitis B core antigen (anti-HBc); a majority of people acutely infected with HBV naturally clear the virus without treatment, conferring immunity against future infection. Infant immunity was defined as presence of antibodies against HBsAg among children age 2 years.

Results

• Among people age 6 years and older, 0.27% had chronic HBV infection, corresponding to approximately 704,000 individuals nationwide.
• 4.6% showed signs of exposure to HBV, corresponding to about 11,993,000 people.
• Current and past infection were very uncommon among children and adolescents age 6 to 19 years.
• 69% of children at age 2 were immune to HBV, mostly due to vaccination.
• Adults -- including groups at high risk for infection -- had much lower rates of immunity.

Based on these findings, the researchers concluded, "A cohort of children and adolescents is growing up in the United States with high rates of immunity against HBV and very low rates of infection."

They noted that the current estimated rates of chronic HBV infection (0.27% vs 0.42%) and exposure with cleared infection (4.6% vs 5.1%) were lower than those reported in a previous survey during 1988-1994.

"Vaccination of high-risk adults should continue to be emphasized," they recommended.

The U.S. Centers for Disease Control and Prevention (CDC) recommends hepatitis B vaccination for all infants at birth, children and adolescents who were not vaccinated as infants, health care professionals and emergency personnel, injection drug users, residents and staff of correctional facilities and group homes, sexually active teens and adults, men who have sex with men, sex partners and household members living with an HBV-infected person, and travelers to countries where hepatitis B is common.

Investigator affiliations: Veterans Affairs Puget Sound Health Care System and University of Washington, Seattle, WA.

3/15/11

Reference
GN Ioannou. Hepatitis B Virus in the United States: Infection, Exposure, and Immunity Rates in a Nationally Representative Survey. Annals of Internal Medicine 154(5): 319-328 (abstract). March 1, 2011.