NEW YORK (Reuters Health) – Among children between 24 and 59 months of age, vaccination with trivalent inactivated influenza vaccine (TIV) is not associated with any serious adverse events, according to a study of data from seven managed care organizations in the US.

“Our results provide additional evidence that TIV is safe in young children,” the authors conclude in their report in the Archives of Pediatrics and Adolescent Medicine.

Dr. Jason M. Glanz, with Kaiser Permanente Colorado in Denver, and colleagues point out that postmarketing surveillance is important for detecting rare vaccine-related adverse events, and that specific safety data for TIV in children aged 24-59 months are lacking.

They therefore identified a cohort of 66,283 children in that age range who received 91,692 TIV shots over four consecutive flu seasons. The temporal relationship of TIV vaccination to medically attended events (MAEs) was examined in a self-controlled analysis; that is, the incidence rates of MAEs in the post-vaccination periods 0-2 days, 1-14 days, and 1-42 days were compared with the incidence in unexposed periods.

Nine types of MAEs had incidence rate ratios greater than 1.0 and met screening criteria. Five of these conditions were considered potentially serious — skin reaction, hypotension, cardiac event, GI tract disorder, and nervous system disorder — and all these occurrences underwent a medical record review. It showed that only one association remained statistically significant, namely, aggregated GI tract disorders in children with a high-risk health condition.

A medical record review of cases reporting the four less serious MAEs – rash, limb soreness, fever, and GI symptoms (diarrhea or vomiting) – confirmed that these conditions were associated with TIV. However, the GI episodes, even in the children with high-risk conditions, were not serious, the authors report.

“We found no evidence of any serious adverse MAEs in TIV postvaccination risk windows of 0 to 2, 1 to 14, or 1 to 42 days,” the team concludes.

A secondary analysis looked at a subset of subjects who had more than one annual TIV vaccination. This showed that the incidence rate ratio of allergic reactions 1 to 3 days after vaccination increased from 6.19 with the second dose up to 16.45 with the fifth dose. However, the dose-response relationship became unclear in an analysis confined to cases confirmed by medical records.

Still, Dr. Glanz and colleagues suggest, “Now that influenza vaccination is universally recommended for all ages, these associations warrant further study in a larger population across a wider age range.”

Arch Pediatr Adolesc Med. 2011;165:749-755.