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Why Does The Flu Vaccine Suck This Year?

Did you get your flu shot? I didn't really want to (I hate needles) but as an infectious disease physician at NewYork-Presbyterian Hospital, it would be exceedingly poor form if I opted out. My job requires it, and I recommend the vaccine to just about every patient, every day. The shot doesn't actually hurt, and if you look at the terrifying data—influenza kills between 3,000 and 50,000 Americans every year—it seems insane not to get immunized. Annual vaccination reduces your chance of dying from the virus by more than 40 percent! But on Wednesday, the Centers for Disease Control announced that this year's vaccine kinda sucks. To be specific, it's less than 50 percent effective against the predominant strain of circulating virus. So what went wrong? It turns out the whole thing is a big guessing game. Influenza vaccines are produced in eggs, and take approximately six months to manufacture, which means scientists start making the flu vaccine in February or March, way before they know which strain is going to be the most problematic. The decision of which strains to include in the vaccine is based upon global surveillance of viruses circulating at the end of the prior influenza season. Scientists are making a guess, but it's an educated guess. The flu shot you got (or will get) covers three or four strains of influenza. The one I received covers three strains (two of influenza A, and one of influenza B), but at the hospital across the street, Memorial Sloan Kettering, they administer one that covers four strains: two A and two B. It's debatable which one is better. This general strategy of vaccine development usually works, but if the virus mutates, or an unexpected strain emerges, you won't be protected. This is not to stay you shouldn't get a flu shot—YOU DEFINITELY SHOULD—but when you do, you really have no idea how much protection it's going to afford you. You see, most studies have overestimated the true efficacy of the flu vaccine. The numbers most frequently quoted are between 70 and 90 percent, but a comprehensive review over nine flu seasons indicates that in adults aged 18 to 64, vaccine efficacy was really only 59 percent, with range of 16 to 76 percent. One study found that the effectiveness of the vaccine during the 2004-2005 was only around 10 percent; two years later, during the 2006-2007 season, that number jumped to 52 percent. This year, the predominant strain of influenza is called H3N2, and preliminary studies indicate the vaccine is a good match for only 48 percent of H3N2 strains. (Influenza A and B are are further subdivided by the characteristics of two proteins called hemagglutinin and neuraminidase; H3N2 refers to subtle variations in these two proteins.) That is to say, this year's shot is performing worse than average, but not much worse. And on the spectrum of underperforming shots, it's still nowhere near the floor. via Why Does The Flu Vaccine Suck This Year?.

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