Tuesday January 27 6:55 PM EST

Poliovirus Vaccine Not Linked To Cancer

NEW YORK (Reuters) -- The tens of millions of Americans who were vaccinated with a contaminated poliovirus vaccine between 1955 and 1963 can breathe a little easier today with the release of new findings that the vaccine does not increase the risk of cancer.

Early on, scientists used monkey kidney cells to produce poliovirus in the lab for the purpose of producing polio vaccines. Many of these kidney cells were contaminated with a monkey virus called simian virus 40, or SV40. But before these researchers discovered that the process they used to kill poliovirus before vaccination did not also kill SV40, millions of Americans were immunized with a vaccine contaminated with the live SV40 virus. Later, in the early 1960s, SV40 was shown to cause tumors in rodents, but it wasn't until the 1990s that the virus was found in rare human tumors of the brain, bone and lining of the abdomen and chest cavities, or mesothelium.

Viral epidemiologist, Dr. Howard D. Strickler of the National Institutes of Health (NIH) in Bethesda, Maryland, and other researchers set out to determine if the risks of these rare cancers were elevated in adults who received SV40-contaminated polio vaccines as children. They combined data collected between 1973 and 1993 in the national epidemiologic study, SEER, information on cancer incidence between 1950 and 1969 from the Connecticut Tumor Registry and national mortality statistics.

What they found was essentially no increased rate of any of the rare tumors in groups of adults known to be exposed to SV40 through contaminated polio vaccine. In fact, the rate of brain tumors was marginally lower in adults exposed as children to SV40, compared with groups of adults not exposed to the virus. On the other hand, the data did reflect an insubstantial "trend" toward an increased rate of cancers of the mesothelium in individuals immunized with contaminated vaccines, though Strickler suspects this trend is more likely related to asbestos exposure than to SV40 exposure.

The new findings are "reassuring," the NIH team says, since "...it is likely that we would have observed an effect on cancer rates if one existed." Strickler and his team believe their findings are "...evidence that no relation exists between exposure to SV40-contaminated vaccine and the development of cancer."
SOURCE: The Journal of the American Medical Association

(1998;279:292-295)

** POSTED JANUARY 28, 1998 **