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).