How do scientists know how to make a flu vaccine if viruses can be different every year?

Updated February 21, 2017 | Factmonster Staff

How do scientists know how to make a flu vaccine if viruses can be different every year?

The flu virus changes every year. However, scientists gather information about virus mutations, or changes, before the flu-virus season begins. This lets them predict what each year’s flu virus might look like. Based on that, a vaccine is made that we hope will be accurate enough to help people fight off major cases of the flu.


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