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Canada Communicable Disease Report
An Advisory Committee Statement (ACS) THIMEROSAL IN VACCINES Adobe Downloadable
Document Preamble The National Advisory Committee on Immunization (NACI) provides Health Canada with ongoing and timely medical, scientific, and public-health advice relating to immunization. Health Canada acknowledges that the advice and recommendations set out in this statement are based upon the best current available scientific knowledge, and is disseminating this document for information purposes. Persons administering or using the vaccine(s) should also be aware of the contents of the relevant product monograph(s). Recommendations for use and other information set out herein may differ from that set out in the product monograph(s) of the Canadian licensed manufacturer(s) of the vaccine(s). Manufacturer(s) have only sought approval of the vaccine(s) and provided evidence as to its safety and efficacy when used in accordance with the product monographs. Introduction Concern has been expressed recently in the Unites States regarding exposure to thimerosal contained in vaccines for American children during the first 6 months of life. This has prompted some provincial and territorial public-health officials to request guidance from Health Canada and NACI on the issue. Thimerosal, a preservative that contains ethyl mercury, has been used as an additive to biologics and vaccines since the 1930s because it is effective in preventing bacterial and fungal contamination, particularly in multidose containers. Background On 7 July 1999, the United States Public Health Service and the American Academy of Pediatrics issued a joint statement recommending that, for infants born to hepatitis B surface antigen (HBsAg) negative mothers, the first dose of hepatitis B vaccine be postponed from birth until 2 to 6 months of age(1). No changes were recommended for infants of mothers who are HBsAg positive or of an unknown status. Consequently, these infants are still administered the vaccine at birth since the risk of developing hepatitis B and becoming a carrier is much higher than the theoretical minimal risk following a bolus injection of thimerosal. In the United States, immunization with other childhood vaccines containing thimerosal remains unchanged. In the United States, the Food and Drug Administration (FDA) Modernization Act of 1997 called for the FDA to review and assess exposure to mercury in foods and drugs. Unlike Canada, most of the routine childhood vaccines in the United States contain thimerosal. Although there is a significant margin of safety incorporated into all acceptable mercury exposure limits, there was concern that some American children could be exposed to a cumulative level of mercury during the first 6 months of life (when most childhood vaccines are administered) that exceeds one of the American federal guidelines on ingested methyl mercury. Although there are no established guidelines specific to ethyl mercury (the type of mercury found in thimerosal) injected into muscle, American experts agreed (at that time) to apply the federally recommended guidelines for exposure to methyl mercury to ethyl mercury as well. In the United States, a thimerosal-free hepatitis B vaccine has been licensed recently (27 August 1999). However, no such product is available or licensed in Canada. Recommendation In Canada, the only thimerosal-containing vaccine included in the regular childhood vaccination schedule is hepatitis B vaccine. Other routine childhood vaccines such as those for measles, mumps, and rubella (MMR) and PentacelTM (for diphtheria, tetanus, acellular pertussis, Haemophilus influenzae type b, and inactivated polio) do not contain thimerosal as a preservative. Hence, Canadian infants are not subject to the same cumulative level of mercury exposure due to vaccine during the first 6 months of life as American infants. There are no scientific data to indicate harm related to the level of exposure to mercury in thimerosal-containing hepatitis B vaccines. Therefore, NACI does not recommend any alteration to the current infant vaccination policies. Moreover, NACI reaffirms the importance of hepatitis B vaccination beginning at birth for high-risk groups(2). These include infants born to HBsAg positive mothers and those at increased risk of acquiring infection during infancy and childhood (e.g. infants of immigrant families from areas with a high prevalence of hepatitis B). If testing is not done during pregnancy, it should be done on an urgent basis at the time of delivery. If maternal hepatitis B virus (HBV) infection status is not available within 12 hours after delivery, consideration should be given to administering HBIG while results are pending, taking into account the mother's risk factors. If the mother is shown to have HBV infection, a series of vaccine doses should also be given. Based on current theoretical assumptions, the amount of mercury exposure through vaccines in Canadian children, even in jurisdictions where there is a routine hepatitis B infant immunization program, is well below even the most conservatively acceptable and tolerable limits. References
* Members: Dr. V. Marchessault (Chairperson), Dr. J. Spika (Executive Secretary), N. Armstrong (Administrative Secretary), Dr. G. De Serres, Dr. P. DeWals, Dr. J. Embree, Dr. I. Gemmill, Dr. M. Naus, Dr. P. Orr, Dr. B. Ward, A. Zierler. Liaison Representatives: Dr. J. Carsley (CPHA), Dr. G. Delage (CPS), S. Donoghue (COHNA), Dr. M. Douville-Fradet (ACE), Dr. T. Freeman (CFPC), Dr. J. Livengood (CDC), Dr. A.E. McCarthy (ND), Dr. J. Salzman (CATMAT), Dr. L. Samson (CIDS), Dr. J. Waters (CCMOH). Ex-Officio Representatives: Dr. A. King (LCDC), Dr. L. Palkonyay (LCDC), Dr. P. Riben (MSB). + This statement was prepared by Dr. P. Varughese and approved by NACI. Our mission is to help the people of Canada maintain and improve their health. Health Canada
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