Stay Out of the Hospital with a Flu Shot

Lower immunity levels from last year’s nearly nonexistent flu season could also hurt us. “Since there was no flu last year, we don’t have any of that natural acquired immunity in our population this year. So that just means we have many more people susceptible which could fuel transmission if and when the season really picks up steam,” says Lauren Ancel Meyers, an epidemiologist at the University of Texas at Austin and director of the UT COVID-19 Modeling Consortium.

Which shot to get

Those 65 and older should get one of two vaccines specifically targeting their vulnerable age group: Fluzone High-Dose and FLUAD. Fluzone High-Dose gives you four times the amount of influenza antigens — the part of the vaccine that helps your body build up protection against flu viruses — compared to the standard dose. The other option, FLUAD, contains an added adjuvant — a substance designed to boost your immune response. Talk to your health care provider about which is right for you.

A flu shot can also help you avoid pneumonia, another respiratory infection that can sometimes piggyback on a system weakened by flu. According to new research, people who got a flu shot earlier this year may be less likely to suffer a severe COVID-19 infection down the road. In one such study, published in the journal Plos One, researchers analyzed the electronic medical records of 74,754 people who tested positive for COVID-19 and found that those who had gotten the flu vaccine during the previous six months were less likely to have had health complications related to their COVID-19 infection.

Doctors typically recommend getting your shot between September and the end of October. Meyers recommends getting your shot on the earlier side this year, where possible. “We don’t know exactly if, when, or how large or how severe this flu season is going to be. But with RSV [respiratory syncytial virus], we saw an unusually early surge in transmission, and the same might happen with flu. Because of that uncertainty, people should absolutely vaccinate, and vaccinating early could provide more protection for individuals and for communities regardless of if and when the virus starts spreading widely.”

In terms of timing, Christensen notes it’s also important to consider when you’ll receive the flu vaccine’s full protection. “After you get the shot, it takes about four to six weeks to build immunity against the flu. Then you get about six months of immunity out of each flu vaccine before the immunity starts to wane.” For this reason, he says, getting your shot in, say, August, could be too early, since protection could wear off while flu is still widespread.

Even if you’re vaccinated, there’s a possibility you could get the flu. You may be exposed to a virus that is not included in the seasonal flu vaccine, since many different flu strains circulate every year. (The overall effectiveness the vaccine ranges from 40 to 60 percent during the years when the vaccine and flu strains match.) 

“We decide on which strains are going to be in the vaccine no later than February or March. But by the time October and November come around, you can have a new influenza virus that is the predominantly circulating strain,” Poland says. “The public might say, ‘The vaccine didn’t work.’ Well, they’re right. But it’s because the virus changed.” Even so, a flu vaccination may lessen the severity of illness if you do get sick. A 2017 study found that the vaccine reduced deaths, ICU admissions and the length of hospital stays among flu patients.

And know this: “Wearing masks, as well as practicing social distancing and hand sanitation, are as effective for the flu as they are for the coronavirus,” says Poland.

What to know about the flu vaccine

Who needs it: All adults, no matter what their age. Be sure to let your health care provider know if you’ve had a severe reaction to the flu shot in the past, are allergic to eggs (the flu vaccine is most commonly grown in them) or have (or have had) Guillain-Barré syndrome (GBS). On rare occasions, people may develop this disorder, in which the body’s immune system damages nerve cells, causing muscle weakness and sometimes temporary paralysis in the days or weeks after getting the vaccination. (Studies suggest, however, that it’s more likely that a person will get GBS after getting the flu itself rather than the vaccination.) If you have a fever, you’ll likely be asked to wait until your temperature is back to normal before you get the vaccine.

How often: Once a year (the sneaky virus itself changes every year). Flu season typically begins in October and ends in March; the CDC recommends rolling up your sleeve by the end of October, since it takes about two weeks after a vaccination for flu-fighting antibodies to develop in the body.

Why you need it: The flu can lead to hospitalization and sometimes death — and older adults are the most vulnerable. Studies show that a vaccination can reduce the risk of falling ill by as much as 40 to 60 percent.

Editor’s note: This article was updated in September 2021 with new information about the 2021-2022 flu season.