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Substantially delaying the first dose of hepatitis B vaccine may lead to underimmunization of children

Many pediatric vaccine schedule changes have been issued in recent years due to vaccine shortages, introduction of new vaccines, and other concerns. For example, the initial birth dose of the three-dose hepatitis B vaccine was suspended in 1999 due to concerns about thimerosal (a preservative in vaccines that is metabolized into ethylmercury). As a result, in practices that delayed the timing of the first hepatitis B dose, fewer children were fully immunized at 24 months. As vaccine policy changes occur, providers should adopt vaccination schedules that minimize delays in the recommended timing of vaccine doses to minimize underimmunization, suggests Nancy D. Lin, Ph.D., of Harvard Medical School and Stanford University.

Dr. Lin and colleagues studied children enrolled in five large U.S. provider groups to evaluate the association between the hepatitis B birth dose suspension and a child's probability of being under-immunized at 24 months. Prior to the hepatitis B birth dose suspension (baseline), the percentage of children who received a hepatitis B vaccination at birth varied widely (3 to 90 percent) across the five provider groups. After the suspension, the percentage of children who received the vaccination at birth decreased in all provider groups.

However, the most substantial decreases in vaccine coverage at 24 months occurred in the two provider groups that shifted the first hepatitis B dose from birth to 5 or 6 months of age. Children in these two provider groups were about three times more likely to be underimmunized for the hepatitis B series at 24 months of age compared with baseline. This trend persisted even after the policy was reversed, with the introduction of the first thimerosal-free hepatitis B vaccine. In contrast, in the three provider groups whose vaccination schedules were unaffected by the birth dose suspension (either due to a combination hepatitis B-Hib vaccine or other reasons), hepatitis B vaccination coverage either was maintained or improved. The study was supported in part by the Agency for Healthcare Research and Quality (HS00028).

See "Variation in hepatitis B immunization coverage rates associated with provider practices after the temporary suspension of the birth dose," by Dr. Lin, Ken Kleinman, Sc.D., K. Arnold Chan, M.D., and others, in the November 13, 2006, Pediatrics 6 (31), which is available at

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