Timely versus delayed early childhood vaccination and seizures.
BACKGROUND
Little is known regarding the timing of childhood vaccination and postvaccination seizures.


METHODS
In a cohort of 323 247 US children from the Vaccine Safety Datalink born from 2004 to 2008, we analyzed the association between the timing of childhood vaccination and the first occurrence of seizure with a self-controlled case series analysis of the first doses of individual vaccines received in the first 2 years of life.


RESULTS
In infants, there was no association between the timing of infant vaccination and postvaccination seizures. In the second year of life, the incident rate ratio (IRR) for seizures after receipt of the first measles-mumps-rubella vaccine (MMR) dose at 12 to 15 months was 2.65 (95% confidence interval [CI] 1.99-3.55); the IRR after an MMR dose at 16 to 23 months was 6.53 (95% CI 3.15-13.53). The IRR for seizures after receipt of the first measles-mumps-rubella-varicella vaccine (MMRV) dose at 12 to 15 months was 4.95 (95% CI 3.68-6.66); the IRR after an MMRV dose at 16 to 23 months was 9.80 (95% CI 4.35 -22.06).


CONCLUSIONS
There is no increased risk of postvaccination seizure in infants regardless of timing of vaccination. In year 2, delaying MMR vaccine past 15 months of age results in a higher risk of seizures. The strength of the association is doubled with MMRV vaccine. 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.
Institute for Health Research, Kaiser Permanente Colorado, Denver, Colorado;Department of Community Health Services, Denver Health, Denver, Colorado;Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado;Department of Epidemiology, University of Colorado School of Public Health, Aurora, Colorado; simon.hambidge@dhha.org.
Simon J
SJ
Hambidge
Institute for Health Research, Kaiser Permanente Colorado, Denver, Colorado;
Sophia R
SR
Newcomer
Institute for Health Research, Kaiser Permanente Colorado, Denver, Colorado;
Komal J
KJ
Narwaney
Institute for Health Research, Kaiser Permanente Colorado, Denver, Colorado;Department of Epidemiology, University of Colorado School of Public Health, Aurora, Colorado;
Jason M
JM
Glanz
Institute for Health Research, Kaiser Permanente Colorado, Denver, Colorado;Department of Pediatrics, University of Colorado School of Medicine, Aurora, Colorado;
Matthew F
MF
Daley
Institute for Health Research, Kaiser Permanente Colorado, Denver, Colorado;
Stan
S
Xu
Institute for Health Research, Kaiser Permanente Colorado, Denver, Colorado;
Jo Ann
JA
Shoup
Department of Epidemiology, School of Public Health, University of Washington, Seattle, Washington;
Ali
A
Rowhani-Rahbar
Kaiser Permanente Vaccine Study Center, Oakland, California;
Nicola P
NP
Klein
Department of Population Medicine, Harvard Pilgrim Health Care Institute and Harvard Medical School, Boston, Massachusetts;Division of Infectious Diseases and Department of Laboratory Medicine, Boston Children's Hospital, Boston, Massachusetts;
Grace M
GM
Lee
Group Health Research Institute, Seattle, Washington;
Jennifer C
JC
Nelson
Department of Research and Evaluation, Southern California Kaiser Permanente, Pasadena, California;
Marlene
M
Lugg
Kaiser Foundation Hospital Center for Health Research, Kaiser Northwest, Portland, Oregon;
Allison L
AL
Naleway
Health Partners Research Foundation, Minneapolis, Minnesota; and.
James D
JD
Nordin
Immunization Safety Office, Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia.
Eric
E
Weintraub
Immunization Safety Office, Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia.
Frank
F
DeStefano
D000367:Age Factors; D002675:Child, Preschool; D015331:Cohort Studies; D005260:Female; D006801:Humans; D007115:Immunization Schedule; D015994:Incidence; D007223:Infant; D008297:Male; D022542:Measles-Mumps-Rubella Vaccine / Q000008:administration & dosage* / Q000009:adverse effects*; D012307:Risk Factors; D012640:Seizures / Q000139:chemically induced* / Q000453:epidemiology / Q000517:prevention & control*; D014481:United States
D022542:Measles-Mumps-Rubella Vaccine
immunization; seizures; vaccine; vaccine delay; vaccine safety