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Poor, misunderstood flu vaccine. It gets no respect: All you ever hear about it is whether it’s a good or bad match for the strain of influenza that’s circulating in a given year, and its dismal effectiveness when there’s a mediocre fit. Unsurprisingly, the vaccine’s bad reputation means poor uptake, which is especially worrisome this year, when we face the possibility of hospitals being swamped by the combined effects of COVID-19 and influenza.

That’s tragic, because the flu vaccine actually has a little known superpower that makes it worth getting — even if you do catch the flu.

The problem is that many people misunderstand the point of the flu shot or a nasal spray vaccine. They think the vaccine’s job is to keep you from catching the flu. And it is — but public health experts also want to keep you from getting seriously ill or even dying. And the vaccine reduces your risk of those bad outcomes, even if you get sick.

How effective is it? One recent study showed the vaccine made an enormous difference for people hospitalized for flu during the 2013-2014 season. Patients who had gotten the vaccine before falling ill — vaccine "failures," in other words — were between 20% and 50% as likely to die as those who’d skipped it. To put it another way, an unvaccinated person who wound up in the hospital because of flu was two to five times more likely to die than someone who’d gotten the vaccine. What’s more, the vaccine made the biggest difference for patients 65 and older, the people most vulnerable to dying of flu.

Other research has shown the same thing. One study that stretched over four flu seasons found that getting vaccinated cut the odds of being admitted to an intensive care unit by 82%. Even among people who got the flu and were sick enough to need hospitalization, the vaccine more than halved the risk of ending up in the ICU.

Of course, the vaccine has another benefit that’s important during a pandemic: It keeps people from needing to go to the hospital. During the 2017-2018 flu season, vaccination prevented some 91,000 flu-related hospitalizations. With COVID-19 cases straining hospitals across the country, flu vaccination is crucial to lighten the burden on doctors and nurses.

These numbers have an important message for those who didn’t get vaccinated against influenza in the 2018-2019 flu season. That’s nearly 55% of adults overall, and 66% of adults in some states. Only 63% of children got at least one dose, even though kids aged 5 and under are at a high risk of serious complications if they get the flu. Last year, young children were hospitalized with flu at the highest rate on record. But parents say one reason they don’t get their children the flu vaccine is that they don’t think it’s very effective.

Colorful flu virus cells with a syringe in the foreground....

Colorful flu virus cells with a syringe in the foreground. File contains meshes. Has companion icons in my portfolio for heart disease, asthma, pharmaceutical research and genetics: Credit: Getty Images/artbyjulie

It’s tough to get the flu vaccine just right. The virus mutates from year to year, and the vaccine production cycle means researchers have to place their bet on which strain will dominate more than half a year in advance. When they choose wrong, a sizable number of people who get the vaccine may come down with flu. But this halo effect changes the calculation about whether it’s worth getting a vaccine that’s just a so-so match.

After all, it’s no fun to get sick — but the real problem with influenza is that it can kill you. If immunization turns a potentially lethal illness into just a few days of garden-variety misery, that’s a "failure" we can all live with.

Dr. Zenobia Brown is medical director and vice president of Population Health Care Management at Northwell Health.