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How long do flu shots protect us for?

Everyone needs to get a flu shot this year. The experts have told us this. But it turns out that flu shots are only effective for a certain amount of time. How do I figure out when I, personally, should get a flu shot so that I can get the maximum protection? Is it based on where I live or my personal risk factors or some complex medical astrology or what? I talked to experts about how to figure out how long flu shots protect us for.

“The best time to get a flu shot is whenever you get one,” says Malia Jones, an epidemiologist and associate scientist at University of Wisconsin. Jones is being pithy — which I deeply appreciate in a medical professional — but what she’s getting at is that this is a better whenever than never situation. That being said, the timing could make a difference. “If you have a choice,” Jones says, “aim for the middle of October, and definitely before Thanksgiving.”

Why October? Because flu season in the United States runs from October to April, and you want your flu vaccination to keep you immune during the peak months. The thing is that the flu shot doesn’t “work” right away. It takes time for your body to respond to the vaccination. “Getting a flu shot in October allows a bit of time for your body to mount an immune response and manufacture antibodies before the season really hits its stride in November,” Jones says.

You want to try your vaccination so that you have immunity when flu season is at its peak, which is generally February in the US. Unfortunately, no one can give you a guarantee about how long your immunity will last. “The exact timeline for immunity waning is not well understood, but it seems to be around 3 to 5 months,” says Jones. So, if you get a vaccination in mid-October and it starts to kick in at the beginning of November, you’ll be covered from November to March, which is kind of the sweet spot.

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The experts I consulted for this article all agreed that the timing of your flu shot does not depend on where you live in the US. But there are some personal demographics that could make a difference. If you’re young, “you don’t want to get your flu shot early, because this can leave you with waning immunity,” says Nate Favini, a San Francisco-based internist. “This can be especially true for people over 65, who don’t tend to have as strong of an immune response to vaccines.” What Favini is saying is that you should probably get your flu shots before your parents do, but he also agrees that getting a flu shot at any time is better than not getting one at all.

But is there going to be a mad rush on flu vaccines this year, given the pandemic? Should we start trying to hoard influenza immunity the way we did toilet paper, in case there’s a shortage? Probably not, Favini says. “Everyone who wants to get vaccinated will likely be able to get vaccinated, so there is no need to panic,” he says. Manufacturers have ramped up production, Favini explains, and the CDC anticipates that we’ll have enough vaccines to immunize 60% of the population here in the US. Only 45% of people get vaccinated in a typical year, Favini says, so we should be good.

I don’t know who needs to hear this, but all of the dozens of experts I spoke with agreed that every single person needs to get a flu shot this year. Why? COVID-19. “A flu shot will not prevent COVID-19, however getting the shot prevents influenza infection,” says Favini. If fewer people will have to go to the hospital for flu-related illness, it will reduce our already overburdened healthcare system, he says, and hospitals and providers will have more resources available to use for coronavirus cases. No one wants to find out what a “twindemic” might be like.

There’s also a psychological benefit to getting a flu shot. “Influenza and COVID-19 have overlapping clinical presentations and symptom lists,” Jones points out. These include fever, body aches, dry cough, and fatigue, she says. That makes it hard for both doctors and laypeople to tell them apart. “If you do come down with the shared symptoms of COVID-19 and influenza, wouldn’t you rather know that you’ve had your flu vaccine? Wouldn’t your doctor want to know?” Jones asks. Yes. Yes. Yes.