Did the polio vaccine (SV40) cause cancer?
Here is what the checked sources say. Each title links to the original.
Vaccine Ingredients: SV40
The contamination really happened: SV40, a monkey virus in the kidney cells used to grow the vaccine, got into US polio vaccine from 1955 to 1963. About 98 million people got the Salk vaccine then, and 10% to 30% of doses were contaminated. SV40 causes cancer in lab animals. But SV40 has been found in cancers of people who never got those vaccines, and studies have not found higher cancer risk in people who got those vaccines, though whether SV40 causes some human cancers is still being studied. US vaccines have been SV40-free since the early 1960s.
Contamination of poliovirus vaccines with simian virus 40 (1955-1963) and subsequent cancer rates
National Cancer Institute researchers compared US birth cohorts likely to have received SV40-contaminated polio vaccine with an unexposed cohort born 1964 to 1969, using over 150 million person years of cancer registry and death data. After more than 30 years of follow-up, exposed groups had no significant increase in brain cancers, bone cancer (osteosarcoma) or mesothelioma. The authors noted the cohorts had not yet reached the age when mesothelioma usually appears.
Cancer incidence in Denmark following exposure to poliovirus vaccine contaminated with simian virus 40
In Denmark, most children got polio vaccine from 1955 to 1961, when it could contain SV40. Across 69.5 million person years of national cancer registry data, people exposed as infants or children had no higher cancer incidence than those born 1964 to 1970, after contamination ended. SV40 exposure was not linked to more mesothelioma, ependymoma, choroid plexus tumors or non-Hodgkin lymphoma. In children aged 0 to 4, ependymoma was higher during the exposed period (RR 2.59, 95% CI 1.36 to 4.92), though incidence peaked in 1969, after the vaccine was cleared of SV40.