The overall rate of effectiveness for the 2015-2016 season’s influenza vaccine is 59%, according to preliminary data shared at a Centers for Disease Control and Prevention’s Advisory Committee on Immunization Practices meeting.
“This means that getting a flu vaccine this season reduced the risk of having to go to the doctor because of flu by nearly 60%,” Dr. Joseph Bresee – who heads the CDC’s Epidemiology and Prevention Branch – stated in a press release. “It’s good news and underscores the importance and the benefit of both annual and ongoing vaccination efforts this season.”
These findings are based on data collected by the U.S. Flu Vaccine Effectiveness Network between November 2, 2015, and February 12, 2016. A 59% effectiveness rate would be roughly in line with what previous years’ vaccines have rated when similar strains of influenza have been prevalent, according to the CDC.
Against the H1N1 strain, which was “responsible for most flu illness this season,” the influenza vaccine was 51% effective. Dr. Bresee noted that the CDC has received reports of unvaccinated individuals this season dying or falling seriously ill because of infection from the H1N1 strain.
The vaccine was 76% effective against all influenza B virus strains, and 79% effective against the B/Yamagata virus strains. There are not enough data at this time, however, to determine the vaccine’s effectiveness against B/Victoria or H3N2 strains.
The CDC cautions that, because the current influenza season is still weeks away from being over, the final rate of vaccine effectiveness for 2015-2016 may change once all the data are analyzed. On average, influenza seasons last 13 weeks.
“Flu activity this season started a bit later and has been lower so far than we’ve seen during the previous three seasons, but activity is still on the upswing and expected to continue for several weeks,” Dr. Bresee stated.