Answer:
Because flu viruses evolve so quickly, last year's vaccine may not protect you from this year's viruses. New flu vaccines are released every year to keep up with rapidly adapting flu viruses.
I have no idea search it up in google
Scientists<span> are working on ways to </span>make embryonic<span> stem </span>cells<span> without destroying </span>embryos<span> and to </span>make cells<span> that </span>behave like embryonic<span> stem </span><span>cells
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