What is SV40 in Vaccines?
SV40 (Simian Virus 40) was an inadvertent contaminant of early poliovirus vaccines produced between 1955 and early 1963, originating from monkey kidney cell cultures used in vaccine production, but modern polio vaccines manufactured after 1963 do not contain SV40. 1, 2, 3
Historical Context of SV40 Contamination
SV40 is a polyomavirus naturally found in rhesus macaque monkeys that was discovered in 1960 as a contaminant in both inactivated (IPV) and oral (OPV) poliovirus vaccines. 2, 3 The contamination occurred because:
- Early vaccine production used primary monkey kidney cell cultures from rhesus macaques that harbored this previously unknown virus 2, 3
- Millions of people received SV40-contaminated vaccines between 1955 and early 1963 before the contamination was identified and eliminated 2, 3
- The virus was eliminated from vaccine production after 1963 by using monkeys bred in isolated colonies and implementing better screening methods 4
Current Vaccine Safety Status
Modern poliovirus vaccines do not contain SV40. The currently licensed IPV products in the United States are:
- IPOL®: Grown on Vero cells (continuous monkey kidney cell line) using the microcarrier method, with no SV40 contamination 1
- POLIOVAX®: Grown on human diploid (MRC-5) cell cultures, eliminating any risk of simian virus contamination 1
Testing of 12 current poliovaccine vials uniformly showed negative results for SV40, confirming that modern production methods using isolated monkey colonies and improved screening have prevented contamination. 4
Clinical Significance and Cancer Risk
Large epidemiologic studies have not identified elevated cancer risk in persons who received SV40-contaminated vaccines, despite SV40 being a known tumor virus in laboratory animals. 2, 5, 6
Key findings from follow-up studies:
- A 35-year follow-up of 1,073 persons who received SV40-contaminated vaccines as newborns found no increased overall cancer mortality (4 deaths observed vs. 3.16 expected) 5
- A case-control study of US Army veterans exposed to SV40-contaminated adenovirus vaccine found no association with brain tumors (OR 0.81), mesothelioma (OR 1.41), or non-Hodgkin's lymphoma (OR 0.97) 6
- While SV40 DNA fragments have been detected in some human tumors by certain laboratories, epidemiologic evidence does not support a causative role 2, 6
Important Caveats
The detection of SV40 in historical vaccines does not affect current vaccination recommendations. Modern IPV is the only recommended polio vaccine in the United States and is completely safe from SV40 contamination. 1, 7
For patients concerned about historical SV40 exposure:
- No special screening or monitoring is recommended for individuals who may have received contaminated vaccines, as epidemiologic data does not support increased cancer risk 5, 6
- Current vaccines pose no SV40 risk and should be administered according to standard CDC/ACIP schedules 1, 7
- The switch to IPV in 2000 was made to eliminate vaccine-associated paralytic polio (VAPP), not due to SV40 concerns 1, 8, 7