The effectiveness of the flu vaccine varies each year. Being 60% effective is considered great. Yet in some years its been lower, such as the 2014-2015 season, when the efficacy was 19%.
This year the CDC reports our trivalent flu vaccine that protects against three viruses (the Influenza A H1N1, H3N2, and Influenza B) is averaging 48% effectiveness. They found against the H3N2 virus, which is the predominant strain this year, the flu vaccine has been 43% effective. And the less common Influenza B virus has been kept at bay 73% of the time. According to the CDC this averages to overall protection of 48%.
Last year the vaccine efficacy was 47% but what’s interesting is the year before last, in which the flu shot was only 19% effective, the flu was dominated by the H3N2 strain. This is the same strain that is predominant this year. Dr. Brendan Flannery, lead investigator for the US Flu Vaccine Effectiveness Network, said, “The prediction for the H3N2 virus was right on in terms of that particular virus continuing to be a dominant virus.”
Vaccines will rarely, when it comes to influenza, reach 90%+ accuracy in that it’s cocktail needs to be determined based on previous seasons’ data and information received from over 100 countries who conduct surveillance of their own.
We usually don’t find out how effective our vaccine is until we peak in the flu season. For the United States the peak is now. Therefore the CDC is urging those who haven’t received the flu vaccine do so now.
For more information on the flu please visit: https://doctordaliah.wordpress.com/2016/10/23/this-years-flu-season-and-flu-vaccine-your-questions-answered/
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Daliah Wachs, MD, FAAFP is a nationally syndicated radio personality on GCN Network, iHeart Radio and Board Certified Family Physician