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Flu Vaccine FAQ

What the CDC Wants You to Know About the 2010-2011 Flu Vaccine

I got the flu during the swine flu pandemic. Do I still need this year's seasonal flu vaccine?

Yes. If you really had the flu during the pandemic, you probably are immune to the H1N1 swine flu. But there are other infections that can mimic influenza, and it could be some other virus that made you sick. Not all infections that act like flu are necessarily flu.

Probably millions of people were infected with the 2009 H1N1 flu strain. But we can't tell which person had swine flu and which had something like flu -- unless they really had a viral-culture test to prove they really had H1N1 virus.

Even then, remember, there is protection against two other flu viruses in this season's vaccine. If you went through having the 2009 H1N1 "swine flu," you certainly don't want to get sick again.

And there's a bonus for people who had an H1N1 infection last year: It will boost their immune response to the H1N1 component of the seasonal vaccine, and they will get additional immunity from the other two components of the vaccine.

I hear the H1N1 swine flu vaccine is included in the seasonal vaccine. Doesn't that make the seasonal vaccine much less safe?

The CDC and the FDA did an enormous amount of monitoring of the 2009 H1N1 swine flu vaccine. After tens of millions of doses, we have no evidence that vaccine was any less safe than any of the vaccines we have used for years.

Our monitoring showed the side effects of the H1N1 vaccine were pretty much the same as you'd see from regular seasonal vaccines. There was no indication the pandemic vaccine was any less safe than any vaccine we've ever produced.

So including that vaccine as one of the three in this year's seasonal vaccine will not change the safety pattern. Even so, we will monitor the safety of this year's seasonal vaccine closely-- as we always do.

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