Immunization Safety Review SV40 Contamination of Polio Vaccine and Cancer (2003) / Chapter Skim
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Executive Summary
Executive Summary
Pages 1-18
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Studies of groups of people who received polio vaccine during 1955-1963 provide evidence of no increased cancer risk. However, because these epidemiologic studies are suff ciently flawed, the Institute of Medicine's Immunization Safety Review Committee concluded that the evidence was inadequate to conclude whether or not the contaminated polio vaccine caused cancer.
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Given the widespread use of vaccines, state mandates requiring vaccination of children for entry into school, college, or day care, and the importance of ensuring that trust in immunization programs is justified, it is essential that safety concerns receive assiduous attention. The Immunization Safety Review Committee was established by the Institute of Medicine (IOM)
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A list of the materials reviewed by the committee, including many items not cited in this report, can be found on the project's website. THE FRAMEWORK FOR SCIENTIFIC ASSESSMENT Causality The Immunization Safety Review Committee has adopted the framework for assessing causality developed by previous IOM committees (IOM, 1991, 1994)
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The IPV produced today uses poliovirus grown on Vero cells, a continuous line of green monkey kidney cells. OPV is no longer produced in the United States, but as the recommended vaccine to control polio outbreaks, a stockpile of OPV is available for these purposes (CDC, 2000)
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Second, it is unclear whether the SV40 received through the vaccine could be transmitted within the population once the contaminated vaccine was no longer in use. SCIENTIFIC ASSESSMENT Causality For its review of the epidemiologic evidence on the association between exposure to polio vaccines containing SV40 and the subsequent development of cancer, the committee found studies examining cancer incidence or mortality.
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Based on these limitations, the committee concludes that the evidence is inadequate to accept or reject a causal relationship between SV40containing polio vaccines and cancer. Biological Mechanisms Given that the epidemiologic evidence regarding a causal relationship was inconclusive, the committee reviewed the biological evidence with an eye to
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Because the Immunization Safety Review Committee was not charged with resolving the full range of uncertainties about the biology of SV40 and the role of this virus in human cancers, the review that follows provides only highlights of the key arguments on these issues. More detailed discussion is available in several excellent and comprehensive reviews (Brown and Lewis, 1998; Butel and Lednicky, 1999, Carbone et al., 1997; Klein et al., 2002; Strickler, 2001b)
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These gene products nonnally suppress tumor growth by preventing cell cycling and by promoting the death of cells with genetic damage. By inactivating these proteins, SV40 Tag promotes both transformation and immortalization of cells.
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Findings Tom studies examining SV40 in mesothelioma demonstrate a great deal of variability which precludes the ability at present to draw conclusions regarding the frequency with which SV40 can be detected in specific neoplasms and/or normal tissues in humans. Some studies have detected SV40 in normal tissue from healthy subjects (Martini et al., 1996; Woloschak et al., 1995~.
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A limited number of people are known to have been exposed to SV40 through other vaccines, including an experimental live-virus vaccine against respiratory syncytial virus and a licensed inactivated adenovirus vaccine that was administered to military recruits. Evidence of SV40 exposure has also been detected in serologic samples obtained before 1955 and from studies of persons too young to have received contaminated polio vaccine.
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The committee's review of the epidemiologic and biological evidence has shown that the effects of exposure to the contaminated polio vaccine remain uncertain, with important questions regarding the role of SV40 in human cancers unresolved. Even if future epidemiologic studies were to provide more compelling evidence for a causal link, the current evidence is sufficiently robust to suggest that the relative contribution of SV40 to overall risk would have to be small.
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The most recent comprehensive plan by the federal government on vaccine safety does not address contamination issues (NIH, 1998~. The committee recommends that the appropmate federal agencies develop a Vaccine Contamination Prevention and Response Plan.
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This will help confirm whether and why SV40 or antibodies specific for SV40 are detected in individuals who have no known exposure to potentially contaminated polio vaccine, animals or laboratory contact. ~ addition to the research recommended above, it is important to resolve the extent of past SV40 contamination of polio vaccine.
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2000. Human mesothelial cells are unusually susceptible to simian virus 40-mediated transformation and asbestos cocarcinogenicity.
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1962. Identification of oncogenic substance in rhesus monkey kidney cell cultures as simian virus 40.
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Transformation induced by simian virus 40 in human renal cell cultures.
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1998. A multi-institutional study confirms the presence and expression of simian virus 40 in human malignant mesotheliomas.
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