Each vaccine contains three influenza viruses-one A (H3N2)
virus, one A (H1N1) virus, and one B virus. The viruses in the
vaccine change each year based on international surveillance and
scientists' estimations about which types and strains of viruses
will circulate in a given year.
About 2 weeks after vaccination, antibodies that provide
protection against influenza virus infection develop in the body.
For information concerning prevention and control please
visit the
CDC website.
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