Poehling KA, et al. - In the United States, quadrivalent live attenuated influenza vaccine (LAIV) and both trivalent and quadrivalent inactivated influenza vaccine (IIV) were available in 2015–2016 season. This study was conducted to assess the vaccine effectiveness of live attenuated and inactivated influenza vaccines in children. Findings suggested LAIV and IIV as effective against any influenza among children aged 2–17 years. Vaccine effectiveness (VE) against influenza A(H1N1)pdm09 was marked for IIV but not LAIV when compared to all unvaccinated children.

Methods

• In accordance to a test-negative case-control design, authors enrolled children aged 2–17 years presenting to outpatient settings with fever and respiratory symptoms for <5 days at 8 sites across the United States between November 30, 2015 and April 15, 2016.
• They obtained a nasal swab for reverse transcriptase–polymerase chain reaction (RT-PCR) testing for influenza, and verified influenza vaccination in the medical record or vaccine registry.
• Using a logistic regression model, influenza vaccine effectiveness (VE) was estimated.

Results

• The analysis retained 1012 children; most of these children (59%) were unvaccinated, 10% received LAIV, and 31% received IIV.
• Authors detected influenza A (predominantly antigenically similar to the A/California/7/2009 strain) in 14% and influenza B (predominantly a B/Victoria lineage) in 10%.
• VE was 46% (95% confidence interval [CI], 7–69%) for LAIV and 65% (95% CI, 48–76%) for IIV for all influenza.
• As per findings, VE against influenza A(H1N1)pdm09 was 50% (95% CI, –2% to 75%) for LAIV and 71% (95% CI, 51–82%) for IIV.
• With RT-PCR–confirmed A(H1N1)pdm09, the odds ratio for vaccine failure was 1.71 (95% CI, 0.78–3.73) in LAIV versus IIV recipients.