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The evidence for the safety of thiomersal in newborn and infant vaccines.

Abstract

While a number of studies remain to be completed, evidence is mounting that there is no demonstrable risk for infants immunized with vaccines containing thiomersal. Epidemiological studies in the US have shown no developmental or other central nervous system abnormalities resulting from exposure to vaccines containing thiomersal. During the initial evaluation of thiomersal in vaccines during 1999, the toxicological profile of ethyl mercury was unknown and presumed to be the same as that of methyl mercury. Enough evidence has accumulated since then to indicate the profiles of the two compounds are different in crucial aspects. To date, one study has measured blood levels of total mercury in vaccinated infants and reports only a brief low-level exposure with rapid excretion of mercury. It is not yet known for sure how much (if any) vaccine-derived ethyl mercury in the blood crosses the blood-brain barrier. For the most part, the use of thiomersal as a vaccine preservative has been convincingly shown to be safe. The scientific evidence is not yet sufficiently strong to provide the same level of assurance for thiomersal-containing vaccines for use in pregnant women or the premature or low birth weight infant. There is an increased sensitivity of the fetal brain to mercury whether it is ethyl or methyl mercury. While there is no evidence to support the contention, it is at least theoretically possible that very low birth weight premature infants may be at increased risk from thiomersal-containing vaccines. Until such time as the scientific evidence is to hand, thiomersal-free presentations of hepatitis B are to be preferred for the birth dose. Given the same levels of exposure, adults are at much lower levels of risk because of increased body mass. It is not possible to prove that thiomersal is completely safe-epidemiology can only quantify a risk, not prove its absence.

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  • Publisher Full Text
  • Authors+Show Affiliations

    Centre for International Health, The Macfarlane Burnet Institute for Medical Research and Public Health Ltd, GPO Box 2284, Commercial Road, Melbourne, Vic. 3004, Australia. john@clem.com.au

    Source

    Vaccine 22:15-16 2004 May 07 pg 1854-61

    MeSH

    Adult
    Animals
    Ethylmercury Compounds
    Female
    Fishes
    Humans
    Infant
    Infant, Newborn
    Infant, Premature
    Infant, Very Low Birth Weight
    Methylmercury Compounds
    Pregnancy
    Preservatives, Pharmaceutical
    Thimerosal
    Vaccines

    Pub Type(s)

    Journal Article
    Review

    Language

    eng

    PubMed ID

    15121295

    Citation

    Clements, C John. "The Evidence for the Safety of Thiomersal in Newborn and Infant Vaccines." Vaccine, vol. 22, no. 15-16, 2004, pp. 1854-61.
    Clements CJ. The evidence for the safety of thiomersal in newborn and infant vaccines. Vaccine. 2004;22(15-16):1854-61.
    Clements, C. J. (2004). The evidence for the safety of thiomersal in newborn and infant vaccines. Vaccine, 22(15-16), pp. 1854-61.
    Clements CJ. The Evidence for the Safety of Thiomersal in Newborn and Infant Vaccines. Vaccine. 2004 May 7;22(15-16):1854-61. PubMed PMID: 15121295.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - The evidence for the safety of thiomersal in newborn and infant vaccines. A1 - Clements,C John, PY - 2003/06/05/received PY - 2003/10/06/revised PY - 2003/11/17/accepted PY - 2004/5/4/pubmed PY - 2004/6/23/medline PY - 2004/5/4/entrez SP - 1854 EP - 61 JF - Vaccine JO - Vaccine VL - 22 IS - 15-16 N2 - While a number of studies remain to be completed, evidence is mounting that there is no demonstrable risk for infants immunized with vaccines containing thiomersal. Epidemiological studies in the US have shown no developmental or other central nervous system abnormalities resulting from exposure to vaccines containing thiomersal. During the initial evaluation of thiomersal in vaccines during 1999, the toxicological profile of ethyl mercury was unknown and presumed to be the same as that of methyl mercury. Enough evidence has accumulated since then to indicate the profiles of the two compounds are different in crucial aspects. To date, one study has measured blood levels of total mercury in vaccinated infants and reports only a brief low-level exposure with rapid excretion of mercury. It is not yet known for sure how much (if any) vaccine-derived ethyl mercury in the blood crosses the blood-brain barrier. For the most part, the use of thiomersal as a vaccine preservative has been convincingly shown to be safe. The scientific evidence is not yet sufficiently strong to provide the same level of assurance for thiomersal-containing vaccines for use in pregnant women or the premature or low birth weight infant. There is an increased sensitivity of the fetal brain to mercury whether it is ethyl or methyl mercury. While there is no evidence to support the contention, it is at least theoretically possible that very low birth weight premature infants may be at increased risk from thiomersal-containing vaccines. Until such time as the scientific evidence is to hand, thiomersal-free presentations of hepatitis B are to be preferred for the birth dose. Given the same levels of exposure, adults are at much lower levels of risk because of increased body mass. It is not possible to prove that thiomersal is completely safe-epidemiology can only quantify a risk, not prove its absence. SN - 0264-410X UR - https://www.unboundmedicine.com/medline/citation/15121295/The_evidence_for_the_safety_of_thiomersal_in_newborn_and_infant_vaccines_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0264410X03008090 DB - PRIME DP - Unbound Medicine ER -