Epidemiology

U.S. adults still have low rates of HBV immunity

Last Updated: 2011-03-01 12:50:23 -0400 (Reuters Health)

By Karla Gale

NEW YORK (Reuters Health) - Kids in the U.S. these days are largely immune to the hepatitis B virus (HBV), but high-risk adults still have low vaccination rates, according to a new study.

And adulthood is the time when exposure to HBV is most likely.

"Adults at high risk of HBV are less likely to be vaccinated (than others), so there needs to be a more concerted effort to reach out to high-risk adults, such as those with HIV, HCV, other sexually transmitted diseases, multiple sex partners, and intravenous drug users," investigator Dr. George N. Ioannou told Reuters Health.

On the other hand, "universal vaccination of infants in the U.S. is working reasonably well," he said. Estimates put complete vaccination rates above 90% of kids aged 19 to 35 months.

Using data on roughly 37,000 participants in the National Health and Nutrition Examination Survey (NHANES), age 6 and older, Dr. Ioannou found that in 1999-2008, 4.6% had serological evidence of HBV exposure, compared to 5.1% in 1988-2004 (p < .001).

Extrapolation of the data shows that currently, 11 million persons in the U.S. have been exposed to hepatitis B, according to his February 28th online paper in Annals of Internal Medicine.

Dr. Ioannou also found that the prevalence of chronic hepatitis B in 1999 to 2008 was 0.27%, lower than the 0.42% prevalence in 1988 to 1994 (p < 0.001).

In the more recent period, the prevalence of chronic HBV was 0.03% or less up to age 17, after which rates climbed to a range of 0.25-0.33% among individuals aged 18 to 49. Peak prevalence was 0.57% for subjects in their 50s, which then dropped back down to about 0.20% among older people.

"We still haven't seen the full benefits of universal vaccination, because in the U.S. most individuals are exposed in adulthood," Dr. Ioannou told Reuters Health. "We're likely to see the greatest effects in the next 10 to 20 years."

He pointed out that even if patients don't develop chronic hepatitis B, exposure to the virus can leave them susceptible to HBV reactivation and at higher risk for cirrhosis and hepatocellular carcinoma.

He also noted that anti-HBs levels declined over time, so the "tough question" will be whether or not booster shots will be necessary.

Dr. Ioannou, from the Veterans Affairs Puget Sound Health Care System and University of Washington in Seattle, found that birth outside the U.S. and Asian race were the most important predictors of HBV infection.

People who were incarcerated or homeless were not included in NHANES, however.

Diagnostic criteria were as follows: for HBV exposure, hepatitis B core antigen antibodies (anti-HBc); for vaccination-induced immunity, hepatitis B surface antigen antibodies (anti-HBs) without anti-HBc; and for chronic infection, HBV surface antigen (HBsAg).

According to the U.S. Centers for Disease Control and Prevention, all infants should get their first dose of HBV vaccine at birth, completing the vaccine series by 6-18 months of age. Older kids up to age 18 who did not get the vaccine when they were younger should also be vaccinated.

The CDC also advises HBV vaccination for high-risk adults, including people who inject street drugs, men who have sex with men, patients with chronic liver or kidney disease (and dialysis patients in particular), HIV patients, and those with:

-- sex partners or household contacts with HBV infection,

-- more than one sex partner, or

-- occupational exposure to human blood.

Also considered to be at high risk are people who live or work in institutions for the developmentally disabled, and those who travel to countries where hepatitis B is common.

SOURCE: http://bit.ly/fu4577

Ann Intern Med 2011;154:319-328.