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Kristina Duda, R.N.

Why Is the Flu Shot "Only" 62% Effective?

By January 15, 2013

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We have seen high levels of flu activity across the country for the past several weeks and the CDC recently declared the flu an epidemic in the United States. Along with the announcement that the flu had reached epidemic levels, the CDC also provided an early estimate that this season's flu vaccine appears to be about 62% effective. This is an early estimate since studies are continuing.

I have heard and read a lot of news reports since the CDC's announcement about the flu vaccine and it's efficacy. Some have states that the vaccine is only 62% effective, which makes it sound like it doesn't work or is less effective than it usually is. That just isn't the case. In fact, as far as flu vaccines go, 62% is actually pretty good. When the strains of influenza in the vaccine are not well matched to the strains that are making people sick, the efficacy of the vaccine can be closer to 30%.

I realize that people are used to getting a vaccine and expecting that they will not get the illness they were vaccinated against. That is how it usually works (although no vaccines are 100% effective) but we unfortunately don't have that kind of coverage with flu vaccines. The flu is unpredictable, can be caused by multiple strains of the virus and mutates all the time. As Dr. Tom Frieden at the CDC said, "the flu vaccine is far from perfect.  But it's still by far the best tool we have to prevent the flu."

So even though getting the vaccine doesn't guarantee that you won't get the flu, at this point it seems you will be about 60% less likely to get it than you would be without it. And perhaps the biggest benefit to getting the vaccine - especially if you aren't in a high risk group - is that you will be less likely to spread it to others who are at high risk. I know many people aren't worried about the flu. You think if you are healthy and young then you don't need to bother with the vaccine because there is little chance that you will experience any complications even if you do get it. But others around you might not be so lucky. And if you can avoid getting it and passing it to other people who may be at high risk, you are helping not only yourself but everyone you come into contact with by getting the vaccine.

Fore more information about how flu vaccines work and why they aren't 100% effective, see:


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