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U.S. Hepatitis B Prevalence in the U.S. in the HBV Vaccine Era

The prevalence of past and present hepatitis B virus (HBV) infection fell by nearly 70% among children in a large household survey of U.S. residents a decade after the introduction of universal HBV vaccination, according to a report by Centers for Disease Control and Prevention (CDC) researchers published in the July 15, 2010 Journal of Infectious Diseases. Hepatitis B prevalence among adults remains high, however, varying considerably among racial/ethnic groups and much greater among foreign-born individuals.

An effective and widely available hepatitis B vaccine (brand names Recombivax HB and Engerix-B, and a combination hepatitis A and B vaccine, Twinrix) prevents HBV infection due to mother-to-child transmission, contact with blood, sexual contact, or other routes.

The HBV vaccine first became commercially available in the early 1980s and was added to the routine infant immunization series in the U.S. starting in 1991, with the first of 3 doses given soon after birth.

Vaccination is also recommended for adolescents who were not vaccinated as babies and for adults at risk, including healthcare and public safety workers, injection drug users, men who have sex with men and all sexually active people who are not in long-term monogamous relationships, travelers to high-prevalence regions, household members of people with chronic hepatitis B, residents of institutions such as prisons and long-term care facilities, and people with chronic hepatitis C (since having both B and C simultaneously can lead to worse liver disease).

Annemarie Wasley from the CDC and colleagues assessed trends in the prevalence of HBV infection in the U.S. after the widespread adoption of hepatitis B vaccination. The investigators determined the prevalence of HBV infection and immunity (due to vaccination or previously having and clearing the virus) in a representative sample of the population during 1999-2006 and 1988-1994 using data from the National Health and Nutrition Examination Surveys (NHANES).

Participants age 6 years and older were tested for antibodies to hepatitis B core antigen (anti-HBc), hepatitis B surface antigen (HBsAg), and antibodies to hepatitis B surface antigen (anti-HBs). Briefly, people who are positive for both anti-HBc and anti-HBs are immune due to natural infection, those who are anti-HBc negative but anti-HBs positive are immune due to vaccination, those who are HBsAg and anti-HBc positive but anti-HBs negative have current infection, and those negative for all 3 markers are susceptible to infection. 

During 1999-2006, the overall age-adjusted prevalence of past and present HBV infection (anti-HBc positivity) was 4.7%.A total of 21,260 NHANES 1988-1994 participants and 29,828 NHANES 1999-2006 participants age 6 and older were interviewed, examined, and tested for anti-HBc and HBsAg. Blood samples were collected for children age 2-5 starting in 1999, but participation in this age group was low with only 3592 total participants, just over half of whom had samples available for testing.

Results

• The 1999-2006 overall age-adjusted prevalence of chronic HBV infection (HBsAg positivity) was 0.27%
• Both of these prevalence rates were statistically similar to those during 1988-1994 (5.4% and 0.38%, respectively).
• The prevalence of anti-HBc positivity decreased significantly among younger people, but not among those age 50 or older:
• Age 6-19: decrease from 1.9% in 1988-1994 to 0.6% in 1999-2006 (P < 0.01);
• Age 20-49: decrease from 5.9% to 4.6%, respectively (P < 0.01);
• Age 50 and older: non-significant increase from 7.2% to 7.7%, respectively.
• During 1999-2006, the prevalence of anti-HBc positivity differed considerably across racial/ethnic groups (all ages combined):
• Whites (non-Hispanic): 2.8%;
• Mexican-Americans: 2.9%;
• Blacks (non-Hispanic): 12.2%;
• "Other," including Asians and non-Mexican Hispanics: 13.3%.
• Anti-HBc prevalence was about 3 times higher among foreign-born participants (12.2%) than U.S.-born participants (3.5%).
• Among U.S.-born children in the 6-19 age group, however, anti-HBc prevalence -- 0.5% overall -- did not differ according to race/ethnicity.
• Disparities between U.S.-born and foreign-born children were smaller during 1999-2006 (0.5% vs 2.0%) compared with 1988-1994 (1.0% vs 12.8%).
• Foreign-born children of "other" race/ethnicity experienced a > 90% decrease in anti-HBc prevalence between 1988-1994 and 1999-2006.
• Among children age 6-19 years, 56.7% showed markers of vaccine-induced immunity, with little difference across racial/ethnic groups.

Based on these findings, the researchers concluded, "HBV prevalence decreased among U.S. children, which reflected the impact of global and domestic vaccination.

However, they continued, HBV prevalence "changed little among adults," and approximately 730,000 U.S. residents are chronically infected.

In particular, they elaborated in their discussion, foreign-born residents made up 14% of NHANES participants during 1999-2006, but accounted for 43% of HBV infections. This type of disparity was not evident among children, however, suggesting that U.S.- and foreign-born residents alike, as well as all racial/ethnic groups, are receiving recommended hepatitis B vaccinations.

"[A] decade after universal vaccination of U.S. children against hepatitis B began in 1991, we demonstrate a significant reduction of 68% in HBV infection prevalence among children, including those born in the United States and elsewhere," the authors wrote. "In addition, a 79% decrease in the prevalence of chronic infection in this age group, although based on a small number of children and not statistically significant, further suggests that substantial progress has been made in reducing the disease burden among children."

With regard to adults, they wrote, "The large burden of chronic HBV infection among adults demonstrated by NHANES highlights the need to improve screening programs and other efforts to identify chronically infected persons, most of whom remain asymptomatic until cirrhosis or end-stage liver disease develops. Screening and counseling programs are important to educate and medically manage infected patients to prevent liver disease progression and to identify and vaccinate susceptible contacts to interrupt further transmission."

National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, GA; National Center for Health Statistics, Centers for Disease Control and Prevention, Hyattsville, MD; School of Public Health, University of Medicine and Dentistry of New Jersey, Piscataway, NJ.

7/2/10

Reference

A Wasley, D Kruszon-Moran, W Kuhnert, and others. The prevalence of hepatitis B virus infection in the United States in the era of vaccination. Journal of Infectious Diseases 202(2): 192-201 (Abstract). July 15, 2010.