No Threat From Tainted
Polio Vaccine?
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.
``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.
The finding, based on a review of mortality statistics and other records, was published in this week's Journal of the American Medical Association.
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.
``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 ...''
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.
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.
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.
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.
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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