TayrcahakeCarole TayrcahakeCarole
  • 21-05-2017
  • Biology
contestada

A flu vaccine is needed seasonally to be effective but a polio vaccine is only needed once. the best explanation of this is ________.

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mona82592
mona82592 mona82592
  • 21-05-2017
The flu has several strains that change seasonally
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shockgamespvp shockgamespvp
  • 21-05-2017
the flu virus code changes often as polio virus does not change at all.

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