MONDAY, Jan. 7, 2019 (HealthDay News) — The quadrivalent live attenuated influenza vaccine (LAIV4) is less effective than inactivated influenza vaccine (IIV) against influenza A/H1N1pdm09 in all pediatric age groups, according to research published online Jan. 7 in Pediatrics.

Jessie R. Chung, M.P.H., from the U.S. Centers for Disease Control and Prevention in Atlanta, and colleagues combined data from five U.S. studies from 2013-2014 through 2015-2016 to compare the vaccine effectiveness (VE) of LAIV4 and IIV among patients aged 2 to 17 years with medically attended, laboratory-confirmed influenza. Data were analyzed by influenza season, subtype, age group, and prior vaccination status.

The researchers found that of 17,173 patients, 4,579 received IIV, 1,979 received LAIV4, and 10,615 were unvaccinated. VE was 67 percent against influenza A/H1N1pdm09 (95 percent confidence interval, 62 to 72 percent) for IIV and 20 percent for LAIV4 (95 percent confidence interval, −6 to 39 percent). When the researchers stratified data by vaccination in the previous season, results were similar. Compared with IIV recipients, LAIV4 recipients had significantly higher odds of influenza A/H1N1pdm09 (odds ratio, 2.66). However, against influenza A/H3N2 and B, LAIV4 and IIV had similar effectiveness. Findings were similar when data were stratified by influenza season and age group.

“From this pooled individual patient-level data analysis, we found reduced effectiveness of LAIV4 against influenza A/H1N1pdm09 compared with IIV, which is consistent with published results from the individual studies included,” the authors write.

Two authors disclosed financial ties to AstraZeneca, and one of the trials was supported by MedImmune, a member of the AstraZeneca Group.

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