Flu Vaccine Nearly 50% Effective So Far This Season — Physician’s First Watch

Medical News |
February 17, 2017

Flu Vaccine Nearly 50% Effective So Far This Season

By Cara Adler

Edited by André Sofair, MD, MPH, and William E. Chavey, MD, MS

The 2016–2017 influenza vaccine has been 48% effective through February 4, according to a CDC analysis in MMWR.

The interim analysis is based on data for 3100 outpatients with acute respiratory illness at five sites across the U.S.; 24% tested positive for influenza.

By virus type, the estimated effectiveness is 43% against influenza A (H3N2), which has caused most infections, and 73% against influenza B. Effectiveness against A (H3N2) varied by age: the vaccine was protective in children aged 6 months to 8 years and in adults aged 50–64, but not in other age groups. So far this season, influenza A (H3N2) viruses match those in the vaccine.

These estimates for influenza A (H3N2) efficacy are similar to those for recent seasons, except 2014–2015, when there was a poor match between vaccine components and circulating virus.

Given that influenza activity remained high as of February 10, the CDC recommends vaccinating unvaccinated individuals aged 6 months and older "as soon as possible."

Reader Comments (1)

John Edwards Emergency Medicine, United States

I'm sorry but reading this study design by no means quantifies the efficacy of the flu vaccine. There has been one double blind controlled trial done in Hong Kong which has shown an entirely different picture of effectiveness. They showed, through correct research methods, a 5 fold increased risk of URI's in TIV individuals.

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