How scientists predict the flu’s viral future

Getting a flu shot is like voting: most people know it’s a thing they’re supposed to do, and yet millions of Americans skip it. In both cases, there’s a lot of apathy involved, and more than a little skepticism: does my vote actually count? Does this flu shot actually do anything?

Well, yes and yes, but let’s focus on flu vaccines.

The path to your shot starts months before you ever see a needle. Twice a year, experts evaluate all the flu strains spreading across the Earth for the World Health Organization. The goal is to predict which strains will hit the population hardest during each hemisphere’s winter. It’s a tough goal, since flu viruses mutate quickly. Based on the WHO analysis, officials from each country decide which flu strains to include in their local vaccine. Then, drugmakers have to actually make the vaccine.

But each season’s shot is essentially a “best guess” at which flu will be circulating that winter. Sometimes the experts are wrong about which viruses will dominate, and that makes the vaccine less effective. (It’s perfectly effective against the strains it was designed to tackle.) During the 2015–2016 flu season, the vaccine basically cut your chances of infection in half: its effectiveness rating was about 48 percent. The year before that, the vaccine was way less effective at only 19 percent.

So does the flu shot do anything to prevent the flu? Absolutely. How much? Your mileage may vary. But the WHO estimates that, around the world, the flu kills 250,000 to 500,000 people each year — and makes millions more seriously ill. That means even a 19 percent effective vaccine is sure to save a lot of lives.

So… get your flu shot! And if you need more convincing, watch our video above.

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