CDC: This Year’s Flu Vaccine is Only 36% Effective

The 2017-2018 influenza vaccine is 36% effective against influenza A and B viruses overall and even less effective against this year's dominant strain, A(H3N2), according to a new report from the Centers for Disease Control and Prevention (CDC).

The report was published following an assessment of influenza-related data on 4562 children and adults enrolled in the US Influenza Vaccine Effectiveness Network. The assessment included statistics from November 2, 2017 to February 3, 2018.
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During this time period, the majority of influenza infections were caused by A(H3N2) viruses. However, this season’s vaccine was shown to be only 25% effective against these types of viruses. In addition, it was found to be only 42% effective against influenza B viruses.

Overall, researchers at the CDC found that the adjusted vaccine effectiveness against influenza A and B viruses associated with medically attended acute respiratory illness during the 2017-2018 season has been 36% thus far.

These statistics have not changed the CDC’s stance on influenza vaccination, however. The agency still recommends receiving this year’s influenza vaccine, noting that it has been more effective against other types of influenza such as A(H1N1)pdm09 viruses (67% effective).

“These early [vaccine effectiveness] estimates underscore the need for ongoing influenza prevention and treatment measures,” the authors of the report wrote. “CDC continues to recommend influenza vaccination because the vaccine can still prevent some infections with currently circulating influenza viruses, which are expected to continue circulating for several weeks.”

—Christina Vogt

Reference:

Flannery B, Chung JR, Belongia EA, et al. Interim estimates of 2017-18 seasonal influenza vaccine effectiveness- United States, February 2018. Centers for Disease Control and Prevention. MMWR Morb Mortal Wkly Rep. 2018;67:180-185. http://dx.doi.org/10.15585/mmwr.mm6706a2.