A number of experts are predicting 10 percent effectiveness for the influenza vaccine this year and attributing it to two main factors: the predictability of the predominant viral strain of flu and the use of eggs to produce vaccines.
According to a November article in the New England Journal of Medicine, flu vaccines are targeted for specific strains of the virus and rely on months-old data.
Each February, the World Health Organization (WHO) uses data compiled over several months to plan which strain to focus on and it takes another six to nine months to deploy the vaccine, according to the journal. However, in some years the predominantly widespread strain of flu has changed after the WHO makes its decision, dampening the effectiveness of the vaccine.
The journal points to the 2014-2015 flu season in the United States, when 80 percent of the cases involved influenza A, but the circulated vaccine targeted a different strain, leaving the vaccine only 13 percent effective.
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