KANSAS CITY, MO. — Almost 1 in 10 foreign-born Asian Americans is chronically infected with hepatitis B virus, according to data from the largest study of hepatitis B infection in Asian Americans to date.
Free serological screening conducted from 2001 to 2006 in 3,163 Asian American adults living in the San Francisco Bay area revealed that 283 (9%) were chronically infected with hepatitis B.
Two-thirds (65%) of those chronically infected were unaware that they were infected, Steven Lin, Ellen Chang, Sc.D., and Dr. Samuel So reported in a poster presentation at the National Immunization Conference sponsored by the Centers for Disease Control and Prevention.
Blood samples were collected by venipuncture and were tested for both hepatitis B surface antigen (HBsAg) and surface antibody (HBsAb), or for HBsAg alone.
The volunteer sample included participants from China (1,016), East Asia excluding China (1,072), Southeast Asia/Pacific Islands (298), the United States (153), other Asian countries (15), and unknown/missing locations (609). The mean age of the participants was 53 years (range, 18–101).
Participants who were born in East Asia, Southeast Asia, or the Pacific Islands were about 20 times more likely to be chronically infected than were those born in the United States (10.7% HBsAg-positive vs. 0.7%, respectively).
Infection rates for each group were as follows: 113 (11%) from China, 103 (9.6%) from East Asia excluding China, 40 (13.4%) from Southeast Asia/Pacific Islands, 1 (0.7%) from the United States, 0 from other Asian countries, and 26 (4.3%) from unknown/missing locations, the investigators said.
Of the 1,523 individuals who were tested for HBsAb, 682 (45%) lacked protective antibodies against HBV and were susceptible to future infection, reported Mr. Lin, a medical student at Stanford (Calif.) University, and his colleagues from Stanford's Asian Liver Center.
Only 381 participants (12%) reported having been vaccinated against HBV. Of these, 20 (5.2%) were found to be chronically infected with HBV. Surprisingly, U.S.-born Asian Americans had a higher risk of being unprotected than did their China-born counterparts (47% vs. 42%).
In December 2006, the CDC published a comprehensive immunization strategy for increasing hepatitis B vaccination coverage among adults, who in 2005 accounted for 95% of an estimated 51,000 new hepatitis B infections in the United States. HBV infection is associated with a 25% risk of death if left unmonitored or untreated. Asian Americans are more than twice as likely to die from liver cancer as their white counterparts are, because of their high prevalence of chronic HBV infection.
“Given the serious medical implications of this study, a strong public health response is needed,” the authors concluded. “In support of the newly released Centers for Disease Control and Prevention recommendations, we call for all foreign-born Asian American adults to be screened for HBV—regardless of their vaccination status.”