Nasal Flu Vaccine Underperforms

January 7, 2019

New research has shown that the live attenuated influenza vaccine (LAIV4) was less effective for the prevention of influenza, especially A/H1N1, compared with inactivated influenza vaccine (IIV).

Previous research into the effectiveness of LAIV4 compared with IIV in children and adolescents has produced inconsistent results.

Using data from 5 US studies from 2013-2014 through 2015-2016, the researchers compared the vaccine effectiveness of LAIV4 and IIV against laboratory0confirmed influenza in patients aged 2 to 17 years.

Of the 17,173 patients included in the study, 4579 received IIV, 1979 received LAIV4, and 10,615 were unvaccinated. Overall, vaccine effectiveness against A/H1N1pdm09 was 67% for IIV and 20% for LAIV4, with similar results when stratified by vaccination in the previous season. Those who were given LAIV4 also had significantly higher odds of contracting influenza A/H1N1pdm09 than those who were given IIV (odds ratio 2.66). Effectiveness against influenza A/H3N2 and B were similar between the 2 vaccines.

“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.”

—Michael Potts


Chung JR, Flannery B, Ambrose CS, et al. Live attenuated and inactivated influenza vaccine effectiveness [published online January 7, 2019]. Pediatrics. doi: 10.1542/peds.2018-2094.

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