MMR Vaccination Does Not Cause SSPE
The MMR vaccine does not increase the risk of SSPE—in fact, vaccination is the only effective prevention strategy for this devastating disease. 1, 2
The Definitive Evidence
The Advisory Committee on Immunization Practices (ACIP) and CDC definitively state that MMR vaccine does not increase the risk for SSPE, regardless of whether the vaccinee has had measles infection or has previously received live measles vaccine. 1, 2, 3
Key Points About Vaccine Safety
When rare SSPE cases have been reported in vaccinated children without known measles history, evidence indicates these children likely had unrecognized measles infection before vaccination, and the SSPE resulted from that natural infection, not the vaccine. 1, 2
Brain biopsy specimens with nucleotide sequencing from vaccinated children who developed SSPE have confirmed wild-type measles virus infection, not vaccine strain. 4
The temporal pattern differs: in children with measles history, SSPE occurred an average of 7.0 years after infection, while in those associated with vaccination (who likely had unrecognized prior measles), SSPE occurred only 3.3 years after vaccination—suggesting the natural infection preceded vaccination. 5
The Actual Risk: Natural Measles vs. Vaccination
Natural measles infection carries a risk of SSPE of 4-11 per 100,000 cases, but this dramatically underestimates the true risk because only 11% of measles infections are officially reported. 3
The risk of SSPE following measles vaccination is 0.5 to 1.1 cases per million doses, compared to 5.2 to 9.7 cases per million following natural measles infection—making vaccination approximately 10 times safer. 5
Widespread measles vaccination has essentially eliminated SSPE from the United States and led to near elimination in countries with high vaccination coverage. 1, 3, 4
In England and Wales, there was an average annual decline of 14% in SSPE onset between 1990-2002, consistent with declining measles cases due to MMR vaccination. 4
Critical Clinical Caveats
Do not confuse SSPE with acute post-vaccination events, which would occur around 10 days after vaccination, not years later. 1
Febrile seizures occur 5-12 days after MMR vaccination at approximately 1 per 3,000 doses and do not lead to residual neurologic disorders or SSPE. 1
At one year after MMR vaccination, a child would be beyond the window for vaccine-related adverse events, which cluster in the first 2-3 weeks. 1
SSPE is caused by persistent wild-type measles virus infection in the brain, not by measles vaccination—the disease mechanism requires natural measles infection. 2, 6
The Public Health Imperative
Recent declines in MMR vaccine coverage have led to increased localized measles outbreaks and cases in young infants, which is of serious concern for SSPE risk. 4
Infants under age 2 years who contract measles are at highest risk for SSPE, with 46% of SSPE cases having had measles before age 2. 5
Maintaining high vaccine coverage protects those most vulnerable to SSPE—namely infants too young to be vaccinated. 4
The only proven prevention strategy for SSPE is measles vaccination. 2, 6