(HealthDay News) – The increased risk of seizures following immunization with measles-containing vaccines is lower when the first dose is administered on schedule at 12–15 months, according to research published online Oct. 14 in JAMA Pediatrics.

Ali Rowhani-Rahbar, MD, MPH, PhD, of the Kaiser Permanente Vaccine Study Center in Oakland, CA, and colleagues analyzed data for 840,348 children to assess the effect of age on the risk of fever and seizures following immunization with a measles-containing vaccine.

The researchers found that the increased risk of seizures at 7–10 days following immunization was significantly greater in children aged 16–23 months than in children aged 12–15 months (relative risk, 6.5 vs. 3.4; attributable risk, 9.5 vs. 4 excess cases per 10,000 doses). The relative risk, but not attributable risk, of post-immunization fever was significantly greater in older than in younger children.

“These results are striking for the additional risk of fever or seizure attributable to delaying vaccination,” write the authors of an accompanying editorial.

Several authors disclosed financial ties to pharmaceutical companies.

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