H1N1 vaccine after H1N1 influenza?

The Pediatric Insider

© 2009 Roy Benaroch, MD

Liz asked about influenza vaccines. If her son already had the flu this year, should he still get a flu vaccine? The regular seasonal one, the H1N1 one, or both?

If Junior got the flu in the United States so far this year, it was almost certainly the novel-H1N1 strain (the so-called “swine flu.”) In ordinary winters, people who have the flu with a specific viral type are protected somewhat against having that same flu again, at least in the same winter. The protection isn’t 100%, but neither is the protection from the vaccine.

But this isn’t an ordinary winter. We don’t really know if people infected with H1N1 have decent immune protection, or how long it will last. And most people who say they’ve had the flu haven’t been tested with a highly accurate test—the office-based, quick test that’s often used is not reliable for knowing for sure that it’s a case of H1N1 influenza.

Studies in past years have shown that giving an influenza vaccine to someone who’s already had the flu doesn’t seem to increase the rate of adverse reactions or problems.

So the CDC recommends (scroll down to the “prior illness” paragraph) that this year, people who’ve been told that they already had the swine flu should still get the H1N1 vaccine. If I were designing a system to vaccinate the highest-priority patients first, I’d figure your son has at least some immunity; so perhaps other, more at-risk kids ought to be vaccinated first. But for best protection for your son and the community, he ought to be vaccinated as well.

But really, for all of us, the best way to get thru this winter is going to be for as many people as possible to get H1N1 vaccines as soon as possible. At a recent national meeting, smart eggheads from the ivory towers of infectious disease told me that their models show that at least half of us in the Unites States are going to get H1N1 influenza this year—the only way to prevent this is if most of us get vaccinated, and quickly, to interrupt transmission of the virus. If the “herd” is mostly immune, the virus will slink away. But if many of us remain un-immune, then there will always be another nice warm body to infect, and then spread to others.

As for the “seasonal” flu vaccine—I think he ought to get that one, too. Seasonal flus other than this novel-H1N1 will start circulating soon, probably by December, and I would hate to think what a regular flu season on top of this H1N1 flu epidemic is going to look like. I got my flu vaccines, and I’m still stockin’ up on Purell!

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Tags: H1N1, immunization, influenza, vaccine

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