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Notice to Readers: Update: Expanded Availability of Thimerosal Preservative-Free Hepatitis B Vaccine

Thimerosal, a mercury-based compound, is no longer used as a preservative in any of the pediatric hepatitis B vaccines licensed in the United States. On March 28, 2000, SmithKline Beecham Biologicals (Rixensart, Belgium)* received approval from the Food and Drug Administration of a supplement to its hepatitis B license to include the manufacture of single-antigen, preservative-free hepatitis B vaccine (Engerix-B, pediatric/adolescent); distribution of this product has begun. A single-antigen, preservative-free hepatitis B vaccine (Recombivax HB, pediatric) from Merck Vaccine Division (West Point, Pennsylvania) had earlier received similar approval (1). A preservative-free Haemophilus influenzae type b (Hib)/hepatitis B combination vaccine (Comvax) from Merck Vaccine Division also is available. An adequate supply of preservative-free hepatitis B vaccine is available for all infant and childhood vaccinations. Thimerosal preservative-containing hepatitis B vaccines may continue to be used for vaccination of adolescents and adults as recommended (2).

Some vaccines that do not use thimerosal as a preservative may have trace amounts of thimerosal introduced during the manufacturing process. The amount of thimerosal in the new pediatric/adolescent formulation of Engerix-B (<1 µg of thimerosal/0.5 mL dose of vaccine) has been reduced by more than 96% (3).

Universal vaccination of infants is the central focus of hepatitis B prevention efforts, and initiation of the hepatitis B vaccine series at birth is safe and effective (4). Many hospitals that had provided routine hepatitis B vaccination to all infants at birth before the July 1999 joint American Academy of Physicians/Public Health Service statement on thimerosal in vaccines discontinued this practice because of concerns about thimerosal (1). Some of these hospitals did not resume routine vaccination at birth even after hepatitis B vaccines that do not contain thimerosal as a preservative became available (CDC, unpublished data, 2000). Preservative-free hepatitis B vaccines are now widely available, and efforts should be made to reintroduce routine hepatitis B vaccination policies for all newborn infants in hospitals in which these policies and practices have been discontinued.


  1. CDC. Availability of hepatitis B vaccine that does not contain thimerosal as a preservative. MMWR 1999;48:780--2.
  2. CDC. Implementation guidance for immunization grantees during the transition period to vaccines without thimerosal, CDC, July 14, 1999. Available at Accessed July 14, 2000.
  3. CDC. Summary of the joint statement on thimerosal in vaccines. MMWR 2000;49:622,631.
  4. Advisory Committee on Immunization Practices. Hepatitis B virus: a comprehensive strategy for eliminating transmission in the United States through universal childhood vaccination. MMWR 1991;40(no. RR-13).

* References to sites of non-CDC organizations on the World-Wide Web are provided as a service to MMWR readers and do not constitute or imply endorsement of these organizations or their programs by CDC or the U.S. Department of Health and Human Services. CDC is not responsible for the content of pages found at these sites.

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