SV40 Virus
Some recent studies have raised the possibility that infection with simian virus 40 (SV40) might increase the risk of developing mesothelioma. Some injectable polio vaccines prepared between 1955 and 1963 were contaminated with SV40. About 10 to 30 million people were probably exposed to the virus.
Intentional infection with SV40 of some laboratory animals, such as hamsters, causes mesotheliomas to develop. Researchers also have noticed that SV40 can cause mouse cells grown in dishes to become cancerous, and that asbestos increases the cancer-causing effect of SV40 on these cells. Other researchers have studied biopsy specimens of human mesotheliomas and detected SV40 DNA. However, similar fragments of SV40 DNA can also be found in noncancerous human tissues and some researchers think the SV40 viruses found are contaminants.
Another study did find SV40 virus in tissues from mesothelioma patients that did not appear to be contaminants. In this study, which also looked at tissue from healthy people, the SV40 virus wasn’t linked to mesothelioma unless the person was also exposed to asbestos. The researchers in this study thought the SV40 infection was not caused by the polio immunization, but occurred naturally as do other viral infections.
So far, the largest studies addressing this issue in humans have not found any increased risk for mesothelioma or other cancers among people who received the contaminated vaccines as children. But, the peak age range for diagnosis of mesothelioma is 50 to 70 years. Some researchers have pointed out that this issue may remain unresolved until more of the people accidentally exposed to SV40 between 1955 and 1963 reach that age range. Research into this important topic is still underway.
A recent study by the Institute of Medicine concluded that we still don’t know whether SV40 is responsible for some mesotheliomas and more research needs to be done.
