This season's flu vaccine is not as effective against the virus as had been previously believed. Health experts had high hopes for this year's vaccine because of changes to the recipe following last season's disappointing success rate. Creating the flu vaccine is not an exact science. Health officials from around the world make their best guesses as to what flu strains to prepare for. They must make their recommendations months in advance so vaccine makers will have time to create and distribute the serum. So far this year, the vaccine has been found to be just 18 percent effective for adults against the H3N2 strain, the dominant strain this season. Officials had hoped for 50 to 60 percent effectiveness for this season's batch.
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