Memories of 1957

Q. Once you have the H1N1 flu, are you immune to it?

A. If you've already had H1N1, you have protection, but only if you're exposed to the same strain of the virus that laid you low. Once your immune system encounters a bug, it creates memory cells that rapidly produce antibodies to fight a second attack of the same bug. That's called acquired immunity, and it's the same process that occurs when you get a flu shot that contains a killed version of the virus.

That sounds great, but the unfortunate fact is flu viruses mutate all the time to avoid the killers, so the next time you encounter H1N1, it might be slightly different and your immune system might not recognize it. But a new study from the Centers for Disease Control and Prevention suggests you still might have partial immunity, so a bout with the new, "improved" H1N1 might not be as severe as your first. The CDC found that those born before 1957 are less likely to get this flu and, when they do, get a mild case because they were previously infected with a similar virus, which left some helpful antibodies behind – not strong enough for a total virus smackdown, but enough to lessen symptoms.

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