HealthDay News — During the 2015 to 2016 season, influenza vaccines reduced the risk of influenza illness, but the live attenuated vaccine was ineffective among children 2 to 17 years of age, according to a study published in the New England Journal of Medicine.

Michael Jackson, PhD, from the Group Health Research Institute in Seattle, and colleagues enrolled patients age 6 months of age or older who presented with acute respiratory illness at ambulatory care clinics. Vaccine effectiveness was estimated using a test-negative design.

The researchers found that 19% of the 6879 eligible participants tested positive for influenza virus, predominantly for A(H1N1)pdm09 and influenza B (11 and 7%, respectively). The effectiveness of the influenza vaccine was 48% against any influenza illness (95% confidence interval [CI], 41 to 55%; P < 0.001).


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The inactivated influenza vaccine was 60% effective among children age 2 to 17 years (95% CI, 47 to 70%; P < 0.001), while the live attenuated vaccine was not effective (vaccine effectiveness, 5%; 95% CI, −47 to 39%; P = 0.80). Among children, vaccine effectiveness against A(H1N1)pdm09 was 63% for the inactivated vaccine (95% CI, 45 to 75%; P < 0.001), compared with −19% for the live attenuated vaccine (95% CI, −113 to 33; P = 0.55).

“Influenza vaccines reduced the risk of influenza illness in 2015 to 2016,” the authors write. “However, the live attenuated vaccine was found to be ineffective among children in a year with substantial inactivated vaccine effectiveness.”

Reference

Jackson ML, Chung JR, Jackson LA,  et al. Influenza vaccine effectiveness in the United States during the 2015-2016 season. N Engl J Med. 2017; 377(6):534-543. 

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