THURSDAY, May 22, 2014 (HealthDay News) -- Postvaccination risk of seizures is increased with vaccinations delayed until the second year of life, according to a study published online May 19 in Pediatrics.
Simon J. Hambidge, M.D., Ph.D., from Kaiser Permanente Colorado in Denver, and colleagues analyzed data from a cohort of 323,247 U.S. children from the Vaccine Safety Datalink (born from 2004 to 2008) to determine the association between the timing of childhood vaccination and the first occurrence of seizure.
The researchers found that in infants there was no association between the timing of infant vaccination and postvaccination seizures. However, after receipt of the first measles-mumps-rubella vaccine (MMR) dose at 12 to 15 months, the incident rate ratio (IRR) for seizures was 2.65, and the IRR after an MMR dose at 16 to 23 months was 6.53. After receipt of the first measles-mumps-rubella-varicella vaccine (MMRV) dose at 12 to 15 months, the IRR for seizures was 4.95, and the IRR after an MMRV dose at 16 to 23 months was 9.80.
"These findings suggest that on-time vaccination is as safe with regard to seizures as delayed vaccination in the first year of life, and that delayed vaccination in the second year of life is associated with more postvaccination seizures than on-time vaccination," the authors write.
Several authors disclosed financial ties to the pharmaceutical industry.
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