Polio Vaccine, and Cancer : Part 3

by CDC

(Page 3 of 3)

In 1999, Fisher and colleagues reported increased rates of ependymomas, osteogenic sarcomas, other bone tumors, and mesotheliomas among people who were potentially exposed to SV40-contaminated polio vaccine. However, the number of cases in this study was too small to draw any statistically valid conclusions.

In 1998, the National Cancer Institute published findings from a study that revealed that, after 30 years, there was no increased incidence of cancer in persons who may have received vaccine containing SV40. The study used the National Cancer Institute's SEER database, which contains information on more than 2.5 million cancer cases in the U.S., and the Connecticut Tumor Registry, and included millions of people exposed to contaminated poliovirus vaccine and decades of cancer incidence and mortality data. Comparisons of the rates of cancer were made between persons who had received SV40-contaminated vaccine as infants born in 1956-1962 and persons born in 1947-1952 and 1964-1969. This study looked specifically for types of rare cancers that have been found to contain SV40 in recent cellular research and found no significant increased incidence compared with persons who had not received contaminated SV40 vaccine. The rare cancers included ependymomas (cancer of cells found in developing fetal neural tubes from which the brain and spinal cord arise as a baby develops), osteosarcomas (a type of bone cancer), mesotheliomas (a type of cancer that originates in the tissue lining of the lung cavity) and brain cancers.

Olin et al. conducted a long-term follow-up study of 700,000 people in Sweden who received polio vaccine potentially contaminated with SV40 in 1957 as school-age children. Their results revealed no increased cancer incidence between persons who received vaccine containing SV40 and those who did not.

Geissler analyzed German National Cancer Registry data to compare the incidence of cancer in 885,783 persons born between 1959-1961 who received polio vaccine that may have been contaminated with SV40 and compared it with 891,321 persons born between 1962-1964 who received SV40 free vaccine. These data demonstrated that persons who received polio vaccine possibly contaminated with SV40 did not develop more tumors within a 20-year period than did those who received vaccine that did not contain SV40.

Mortimer studied cancer deaths of 1073 persons born between 1960-1962 who received oral poliovirus or inactivated poliovirus vaccine that contained SV40 when newborn. The follow-up study over 17-19 years revealed no increased number of deaths from cancer. In 2001, a thirty-five year follow-up study of this group was published. The study found no deaths in the group due to tumors of the type that have been associated with SV40.

Fraumeni et al. followed 1000 persons who had received SV40 contaminated poliovirus vaccine within a few days after birth. The majority of these people received the SV40-contaminated oral vaccine. At eight years of age, no cancer deaths were identified in the exposed group.

Fraumeni et al. focused on a cohort of children age 6-8 years who received inactivated poliovirus vaccine in 1955. A comparison was made based on whether children received vaccine with high, low or no detectable amount of SV40 contamination. Mortality rates from leukemia and all other cancers from 1950-1959 were compared across the three groups. No differences in cancer rates were found for this period.

In summary, the majority of studies in the U.S. and Europe that compare persons known or strongly presumed to have received SV40-contaminated polio vaccine with those known or strongly presumed not to have received SV40- contaminated polio vaccine have not shown a causal relationship between receipt of SV40-contaminated polio vaccine and cancer. It should be noted, however, that SV40 infection has been found in persons who did not receive SV40-contaminated polio vaccine and that for some study participants it cannot be known with certainty whether or not they received SV40-contaminated vaccine. Because of this, there may be errors in these studies that make it harder to detect a true increased cancer risk associated with receipt of SV40-contaminated polio vaccine. In addition, research is needed that focuses on the long-term consequences of SV40 exposure, as some cancers like mesotheliomas typically occur later in life and would not have been detected in several of the studies described above. Moreover, additional studies are needed which focus on the potential long-term effect of SV40 exposure on health outcomes other than cancer. Because the CDC takes this issue very seriously, the agency has asked an expert committee to review the existing data on this topic and provide recommendations for future research.

Have research studies looked at the risk of cancer in children whose mothers received SV40-contaminated polio vaccine?

Yes, two studies concerning maternal vaccination with SV40-contaminated vaccines and risk of cancer in offspring have been conducted. Each study reported an association.

1. Heinonen et al. reported a higher incidence of neural malignancies in children born to mothers who received inactivated poliovirus during pregnancy. The prospective study of over 50,000 women who were pregnant between 1959-1965 identified 24 malignancies in their children during the first 4 years of life. The rate of malignancy was about two-fold greater in children born to mothers immunized during pregnancy when compared with children born to unimmunized mothers or mothers who received influenza or OPV vaccines. Neural tumors accounted for most of the difference. 2. Farwell et al. found that of 15 cases of medulloblastoma in children born in Connecticut between 1956-1962, 10 were born to mothers exposed to SV40 contaminated polio vaccine while 5 were born to mothers unexposed. Interpretation of these results, however, is hampered by the low response rates and uncertain accuracy of vaccination histories by obstetricians.

Additional studies are needed that focus on maternal vaccination with SV40-contaminated vaccines and risk of cancer and other health effects in offspring.

If I have one of these cancers does it mean that SV40 caused it?

No. The possible role of SV40 in human cancers is not fully understood and is the topic of continued research.

Can I obtain a test to see if I am infected with SV40?

Blood tests can identify if a person has antibodies to SV40, but there is no test for SV40 commercially available at this time.

Research laboratories are currently refining the techniques used to detect SV40. PCR (polymerase chain reaction) assays are currently in use to detect SV40 DNA segments. Because of inconsistent results between laboratories, there is a need to develop a standard PCR assay.

What should I do if I received polio vaccine during 1955- 1963?

There are no recommended treatments or tests for persons that may have been exposed to SV40. If you have concerns about your health, please make an appointment to see your health care provider.

About the Author

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