The rates of HBV exposure and chronic infection were significantly lower in 1999–2008 than in 1988–1994; 2-year-olds had higher immunity rates than adults.
Hepatitis B virus (HBV) is the most common cause of liver disease worldwide. HBV-associated morbidity and mortality are substantial in the U.S., even though prevalence of the virus is lower here than in some other areas. Infant immunization against HBV has been recommended since 1991, and from 2004 to 2009, about 94% of U.S. children aged 19 to 35 months received all three vaccine doses. Have the rates of immunity and chronic infection changed in recent years?
To answer this question, a researcher examined National Health and Nutrition Examination Survey (NHANES) data. From 1999 through 2008, 39,787 participants aged 2 years were tested for serum antibody to hepatitis B surface antigen (anti-HBs), and 37,259 individuals aged 6 years were tested for antibody to hepatitis B core antigen (anti-HBc) and for hepatitis B surface antigen (HBsAg). Exposure to HBV was defined as a positive anti-HBc result; chronic HBV infection, as a positive HBsAg result; and vaccine-induced immunity, as a positive anti-HBs result in the absence of anti-HBc (or, in children aged 2–5 years, a positive anti-HBs result alone).
Of participants aged 6 years, 4.6% had been exposed to HBV (95% confidence interval, 4.1%–5.0%), and 0.27% had chronic HBV infection (95% CI, 0.20%–0.34%). The rates were significantly lower than those estimated by NHANES III for 1988 to 1994 (5.1% and 0.42%, respectively). Children aged 2 years (old enough to have completed HBV vaccination) had a very high rate of immunity; adults — including those at high risk — did not.
Comment: Although the rates of chronic disease and immunity are heading in the right directions, the improvements seem modest. However, exposure and infection rates may have been misestimated because of sampling problems. For example, recently arrived or unauthorized Asian immigrants (a very-high-prevalence group) may have been undersampled, and homeless and incarcerated persons (another high-prevalence group) were not included. The author emphasizes the need to immunize high-risk adults.
— Stephen G. Baum, MD
Published in Journal Watch Infectious Diseases March 2, 2011
