By Dr. Sanjay Gupta
Chief Medical Correspondent

Everywhere I go, people tell me "Hey Doc, I got the flu shot and I still got sick!" And, given that I do recommend the flu shot as a physician, they seem to hold me somewhat responsible. Even though I have nothing to do with actually designing the flu vaccine, I get it. And, I do feel bad. I hate seeing people sick. Truth is, this year I may get more of those comments than in years past. The flu season is getting pretty bad with 49 states now reporting widespread flu activity. No surprise given that this year's vaccine is only 40 percent effective. Let me explain.

What you may not know is that developing a flu vaccine is largely guesswork. That's right; it is more speculation than science. Last year sometime, scientists were asked to predict what strains of the flu would be most problematic this year. It's kind of like hitting a moving target, as the virus strains change constantly. The scientists typically choose three strains, two from the type A family and one from the Type B family. The flu shot you get is designed to protect you against those three strains.

For frame of reference, 16 of the last 19 years, the scientists' predictions were good ones. While those vaccines in years past were not perfect, they were between 70 percent and 90 percent effective. This year, though, they missed the mark, most specifically with that B strain, and people are getting sick.

I know it sounds crazy, but there is method behind the madness. The way vaccine production works, it takes about six months to make enough for everyone who needs the shot. If scientists and vaccine-makers waited to learn exactly which strain of virus is circulating, there wouldn't be enough time to produce the vaccine. They're working on better, faster methods, but none are ready to implement.

Plans for next year's flu vaccine have already begun, and the World Health Organization is recommending some big changes. Of course, this is of no comfort to people who are suffering right now.

So, do you have any ideas on how to better protect ourselves against the flu? Given the background on the flu vaccine, are you more or less likely to get the shot?

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