The Claim:
What’s old is new again. SV40, a simian virus that raised some concern about cancer once upon a time, is now being found in mRNA vaccines, according to a Japanese report on Twitter.
The Facts:
SV40 is a virus found in monkey kidneys that can potentially cause cancer in humans via tumor (T) antigens. Unfortunately, batches of the polio vaccine became contaminated with SV40, and the methods used to inactivate the poliovirus did not reliably inactivate SV40. Importantly, epidemiological studies have found no increased risk of cancer in those who received these vaccines.
Since then, a promoter gene (a DNA sequence that starts RNA transcription) of SV40 has been found to promote a high level of gene expression for producing proteins in mammalian cells and has been used in developing DNA vaccines. The process uses just the promoter gene and not the virus itself or any part of the DNA sequence that encodes for the T antigen of SV40.
Right now, no evidence exists that mRNA COVID vaccines contain SV40 genes, aside from a single paper that has claimed to sequence the SV40 promoter gene from the Pfizer vaccine.
Disclaimer: Science is always evolving and our understanding of these topics may have evolved too since this was originally posted. Be sure to check out our most recent posts and browse the latest Just the Facts Topics for the latest.
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