Researchers call for further data on incremental dosing of TIV in younger children

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

Issue: September 2011

Children aged 2 to 5 years did not appear to have an increased rate of serious medically attended events after receiving the trivalent inactivated vaccine, but risk for vaccine and allergic reactions may increase incrementally with subsequent doses, according to a paper published online.

Jason M. Glanz, PhD, and colleagues of the Kaiser Permanente Colorado Institute for Health Research analyzed data for more than 66,000 children who received more than 91,000 doses of TIV at seven health facilities.

According to the researchers, 142 medically attended events may have been related to the vaccine, but only four were deemed statistically significant, and none of those were deemed serious with 42 days of follow-up. Fever, limb soreness and gastrointestinal illnesses were the most common issues associated with the vaccinations, according to the study findings. However, the researchers said they did not rule out the possibility that the gastrointestinal illness may have been related to stomach virus infection that the children may have acquired at their physician’s office while awaiting influenza vaccination.

“An apparent dose-response relationship was observed in the electronic analysis for vaccine and allergic reactions in the 1- to 3-day risk window. Biologically, it is possible that certain subpopulations become susceptible to vaccine reactions after multiple annual exposures,” the researchers said, adding that such a scenario has been noted with the diphtheria and tetanus toxoids and acellular pertussis vaccines.

This possible association should be studied further, and analytic methods will be required to gather this type of data, according to the researchers.

Study limitations included, specifically, that the analyses were based on managed care administrative data, so “it is possible that many of the medically attended events were misclassified and did not represent true incident cases,” they said.

Regardless, the investigators said their results “provide additional evidence that TIV is safe in young children.”

Disclosure: The researchers report no relevant financial disclosures.

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