- CHICAGO (Reuters) - Polio vaccine contaminated with a monkey virus
and administered to millions of people four decades ago does not appear
to be causing some rare forms of cancer, a study said Tuesday.
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- ``The absence of a discernible effect
in our study adds to the evidence that no relation exists between exposure
to (the contaminated) vaccine and the development of cancer. As the exposed
cohorts mature, however, it will be important to continue monitoring of
cancer risks,'' researchers at the National Cancer Institute said.
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- The finding, based on a review of mortality
statistics and other records, was published in this week's Journal of the
American Medical Association.
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- The investigation was prompted by the
recent detection of DNA from the same monkey virus in several rare human
tumors affecting the brain, bones and the lining of the lung and chest
cavity.
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- ``Our study failed to detect any significant
increases in the risk of cancers reported to contain (monkey virus) DNA
among the birth cohorts exposed to (the) contaminated vaccine,'' the study
said. ``In effect (the tumors) have remained rare cancers ...''
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- Injections of the vaccine were given
to tens of millions of people in the United States alone between 1955 and
1963. By 1961 between 80 percent and 90 percent of all U.S. children and
adolescents under the age of 20 had been injected. In 1963 a different
form of vaccine given in oral doses replaced the injections and it did
not have the monkey virus contamination.
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- The virus, which can cause cancer in
rodents, got into the vaccine because early preparations used kidney cell
cultures from Asian monkeys in the process of making the vaccine.
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- The report added, however, that the monkey
virus, called simian virus 40, is a human pathogen that could have gotten
into the population by other routes. It is possible the virus has tumor-causing
potential ``in humans exposed under different conditions and higher levels
of virus than were associated with poliovirus vaccine,'' it added.
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- It also said a study done in Germany
and published in 1990 also found no significant differences in cancer rates
among more than 885,000 people exposed there to the same contaminated virus
when compared to people born a few years later who received the oral non-contaminated
vaccine.
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- But that study, it said, did not check
for the rare human tumors to which the virus has been linked more recently.
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