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ACAAI > Patients & Public > Resources > Ask the Allergist

Flu Vaccines

Q:  "My nurse looked at this year’s respiratory flu vaccine and found it has H1N1 already in it — isn’t that the same as swine flu?"

A:  She’s right! The terminology is a little confusing but here’s a refresher: H1N1 is a subtype of Influenza A that has caused roughly half of all human flu infections we’ve seen in the past several years. H1N1 viruses are identified by two surface proteins: Hemagglutin (H) and Neuramidase (N). The strains H 1, 2 and 3, and N 1 and 2 are found in people - a lot more strains are found in birds and pigs. Your nurse is right. This year’s respiratory flu does contain several H1N1 strains. But this year’s "swine flu" or H1N1 flu results from reshuffling of four different flu viruses – North American swine influenza, North American avian influenza, human influenza, and swine influenza virus usually found in Asia and Europe. Maybe we do get some general crossover protection with the regular respiratory flu shot or mists — but you can’t get specific protection with anything but the new additional flu shots.

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