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Prenatal HBV screening, neonatal treatment reduced vertical transmission
A community-based program of prenatal hepatitis B virus screening followed by neonatal immunoprophylaxis was highly effective in preventing vertical transmission of the infection, according to new study results.
“Because 35% to 50% of carriers are believed to be infected by perinatal exposure to blood or blood-contaminated fluids, the prevention of vertical transmission from mother to child plays a vital role in decreasing disease prevalence,” researchers wrote in the Annals of Internal Medicine. “Approximately 24,000 HBV-infected women give birth annually in the United States, which makes their offspring an important at-risk population.”
The CDC recommends HBV screening in pregnant women and the provision of HBV immunoglobulin (HBIg) and HBV vaccination for infants of HBV-positive mothers within 12 hours of birth and two additional doses of the vaccine within the next 6 months.
“The CDC guidelines work for the majority of infants in preventing vertical transmission if the immunizations are done according to the recommended schedule,” study researcher Ai Kubo, PhD, an epidemiologist with the Kaiser Permanente Division of Research, told Infectious Disease News.
Ai Kubo
Kubo and colleagues from Kaiser Permanente studied the effectiveness of a community program that implemented the CDC’s recommendations. The Kaiser Permanente Northern California (KPNC) Regional Perinatal Hepatitis B program has been tracking all pregnant women with HBV and their exposed infants for the past 25 years, following up with providers to make sure patients received appropriate treatment to prevent transmission of the virus. According to Kubo, the program has led to nearly complete immunization coverage.
“This is important, as without an organized effort, immunization and follow-up rates can be low and there is a greater chance of transmission,” she said.
The study included 4,446 infants born within KPNC health services to 3,253 HBV-positive mothers between 1997 and 2010. The researchers examined rates of vertical transmission, adherence to immunoprophylaxis, follow-up testing rates and maternal risk factors for HBV transmission to infants.
Among the entire infant cohort, 0.75% were hepatitis B surface antigen (HBsAg)-positive (n=25) — an infection rate of 0.75 per 100 births (95% CI, 0.48-1.1). Among children born to e antigen-positive mothers, the overall infection rate was 3.37 per 100 births (95% CI, 2.08-5.14). Among those born to e antigen-negative mothers, only one infant with an unknown viral load was infected with HBV, a rate of 0.04 per 100 births (95% CI, 0.001-0.24).
According to the researchers, the lowest viral load associated with vertical transmission was 6.32x107 IU/mL. Among 831 women with viral loads <5x107 IU/mL, the infection rate was 0 — regardless of e antigen status. Among 83 births to mothers with extremely high viral loads (≥5x107 IU/mL), there were three transmissions (ie, infection rate of 3.61 [95% CI, 0.75-10.56]).
“The highest risk of transmission was observed among mothers with extremely high viral loads and e antigen positivity,” Kubo said. “This group of women may benefit from additional therapy to prevent vertical transmission. However, for others, the risk of transmission is extremely low as long as the infants are immunized according to the guidelines.”
According to Kubo, the results underscore the importance of tracking and administering immunizations to infants, as well as identifying high-risk mothers who may benefit from additional therapy. However, a centralized approach such as the one described in the study may be difficult to implement in many prenatal care settings.
“It takes an organized effort to screen all mothers, identify HBV-positive mothers, and track every infant to ensure that everyone is receiving the immunizations on time,” Kubo said. “This type of effort was possible for Kaiser Permanente because it is an integrated health delivery system, but this may not necessarily be easy to implement in other settings.” – John Schoen
Ai Kubo, PhD, can be reached at 2000 Broadway, Oakland, Calif. 94612; email: ai.kubo@kp.org.
Disclosure: See the study for a full list of researchers’ financial disclosures.