Preliminary influenza vaccine effectiveness for the 2015-2016 flu season is 59%, according to data presented by the Advisory Committee for Immunization Practices (ACIP).

The ACIP also reported 51% vaccine effectiveness against the H1H1 virus, responsible for most instances of flu illness during the 2015-2016 flu season; 76% vaccine effectiveness against all influenza B viruses; and 79% vaccine effectiveness  against the B/Yamagata lineage of B viruses. Insufficient data exist to estimate vaccine effectiveness  by age group or against H3N2 and B/Victoria lineage viruses. Existing estimates are based on data collected by the U.S. Flu Vaccine Effectiveness  Network between November 2, 2015, and February 12, 2016.

“Flu activity this season started later and has been lower so far than what we’ve seen during the previous three seasons,” said Joseph Bresee, MD, chief of the CDC’s Epidemiology and Prevention Branch. “But activity is still on the upswing and expected to continue for several weeks.”

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Seasonal influenza activity has been elevated for 5 consecutive weeks; the past 13 seasons have averaged 13 weeks in length.

The CDC recommends annual flu vaccination as the best method to prevent seasonal influenza and encourages rapid treatment of ill and high-risk suspect flu patients with influenza antiviral drugs.


  1. Flu vaccine nearly 60 percent effective [news release]. Atlanta, GA: Centers for Disease Control and Prevention. Published February 24, 2016. Accessed February 26, 2016.