Febrile Seizure Risk After Vaccination in Children 6 to 23 Months

Area of Science:

• Pediatric Vaccinology
• Immunology
• Epidemiology

Background:

• Febrile seizures (FS) are a concern in young children post-vaccination.
• Previous findings suggested an increased FS risk with co-administration of trivalent inactivated influenza vaccine (IIV3) and pneumococcal conjugate vaccine (PCV) 13-valent.

Purpose of the Study:

• To investigate if co-administration of IIV3 with other routine vaccines impacts FS risk in children aged 6-23 months.

Main Methods:

• A population-based self-controlled risk interval analysis was employed over five influenza seasons (2006-2011).
• Risk intervals were analyzed for 0-1 day post-vaccination compared to a control interval of 14-20 days post-vaccination.
• Multivariable regression controlled for concomitant vaccines and tested for interactions.

Main Results:

• Pneumococcal conjugate vaccine (PCV) 7-valent showed an independent FS risk (IRR 1.98).
• IIV3 alone did not show an independent risk (IRR 0.46).
• Concomitant IIV3 with PCV or DTaP-containing vaccines significantly increased FS risk (IRR 3.50 for both). The excess risk was estimated at 30 FS per 100,000 persons.

Conclusions:

• Administering IIV3 on the same day as PCV or DTaP-containing vaccines is associated with a higher risk of FS compared to separate administration days.
• The absolute risk of post-vaccination FS with these combined vaccine schedules is low.
• Consideration of separate vaccination days for IIV3 with PCV or DTaP vaccines may be warranted to minimize FS risk.