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CDC: Flu vaccine effectiveness low, antiviral use crucial
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This season’s influenza vaccine offered reduced protection, having an estimated vaccine effectiveness of 23%, according to data published in MMWR.
“Physicians should be aware that all hospitalized patients and all outpatients at high risk for serious complications should be treated as soon as possible with one of three available influenza antiviral medications if influenza is suspected, regardless of a patient’s vaccination status and without waiting for confirmatory testing,” Joseph Bresee, MD, branch chief of CDC’s Influenza Division, said in a press release. “Health care providers should advise patients at high risk to call promptly if they get symptoms of influenza.”
According to the report, the adjusted, age-specific vaccine effectiveness ranged from 12% for people aged 18 to 49 years to 26% for children aged 6 months to 17 years. For adults aged 50 and older, the vaccine effectiveness was 14%.
Early estimates of vaccine effectiveness are available this year because of early widespread circulation of influenza, officials wrote in the report. The interim vaccine effectiveness measure is low compared to previous seasons, because the predominant circulating H3N2 strain is different from the H3N2 strain included in this year’s vaccine.
So far this season, most influenza infections were due to H3N2, but more than two-thirds of the H3N2 viruses circulating are similar to the A/Switzerland/9715293/2013 (H3N2) virus, which is a component of the Southern Hemisphere influenza vaccine. The Northern Hemisphere vaccine contains A/Texas/50/2012 (H3N2).
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