Flu shots work, and are a smart way to reduce the chances that you’ll end up sick this winter (especially if you get the new COVID booster too while you’re at it). But that’s not the impression you might get if you listen to the rumor mill, online or otherwise.
Flu shot myths abound, and it’s time to put the four biggest ones to rest.
Myth: The flu shot doesn’t work
The flu vaccine isn’t perfect, but you’re still better off getting it than not. In a good year, the flu vaccine is about 70 percent effective; if we’re unlucky, the rate can dip lower, but it still offers some protection.
Last year’s flu shot was 59%-67% effective for kids and 33%-49% effective for adults. (There were multiple studies done, which the CDC collected in a report here.) The exact effectiveness varies from year to year, with better years over 60% effective overall, and less-good years closer to 25%. We won’t know the effectiveness of this year’s shots until flu season is over, but clearly flu shots reduce the odds that you’ll get the flu, and they also prevent hospitalizations from severe cases.
The CDC has the receipts on all the ways flu shots result in people being healthier and at less risk of severe illness or death. They highlight research that confirms that flu vaccines result in less flu illness, reduced risk of hospitalizations from the flu, reduced risk of heart and lung disease in people with those health conditions, reduced flu illness in people who are pregnant (while also protecting their babies after birth), and significantly reduced risk of children dying from the flu. Plus, the shot helps to prevent the spread of flu—so even if you aren’t worried about your own health, getting a flu shot means it’s harder for the virus to use you as a stepping stone to infect others.
So why are flu shots not always effective? Other vaccines have better track records; the measles vaccine is 97 percent effective, for example, in children who get both of the recommended doses. Here are a few reasons the flu vaccine is an odd case:
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There isn’t just one type of flu. Flu viruses mutate a lot, so we need a new shot every year. The people who make flu shots have to choose in the spring which strains should go in the shot for that fall and winter, and if they guess wrong, the shot will be less effective. (That’s what happened in 2014, when the shot was only 23% effective.)
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Some people don’t respond well to the vaccine. Flu shots are less effective in children under age 2, and adults over 65 (although high-dose, adjuvanted, and recombinant shots can make up some of that gap for older adults). Other factors and health conditions can affect how well you’ll respond.
Because effectiveness varies so much, scientists, including those at the CDC, keep tabs on what strains of flu are circulating and how the vaccine currently fares against them. When they change their recommendations it can look like a flip-flop, but they’re really just staying on top of the best available information. For example, nasal flu vaccines were pulled from the market for a few years because they were’t providing enough protection, but the current version of that vaccine is improved enough that it’s recommended for the general public once again.
Myth: I don’t need a flu shot
Depending on the year, about 8% of Americans get the flu each year. The people at greatest risk of getting sick or dying from the flu are young children, the elderly, and people with underlying health problems. But healthy people are just less likely to get seriously ill; they’re not invincible.
Flu symptoms can include fever, cough, and sore throat, so they’re similar to the symptoms of colds, COVID, and other respiratory illnesses. That means plenty of people think they’ve had the flu when really they’ve had something else. Ask anyone who’s had a confirmed case of influenza: flu knocks you on your ass, with fatigue and body aches that last a week or more.
And, not to get too morbid, but people really do die from the flu: Last year, 5,944 of them. In general this figure can be anywhere between 3,300 to 49,000 per year. For comparison, around 30,000 people die in car crashes.
There’s another important reason to get a flu shot, even if you’re healthy: Every person who is susceptible to the flu is a stepping stone the virus can use to reach the elderly and sick. Those people are the most vulnerable to flu complications like pneumonia—and the most likely to die from flu.
Myth: The flu shot can give you the flu
This is a persistent myth, and it’s just plain wrong. Flu shots do not contain fully functioning flu viruses. Depending on which version of the flu vaccine you get, it contains either:
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Chopped up flu viruses (most of the injectable vaccines)
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An isolated protein from the flu virus (recombinant vaccines)
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An attenuated (weakened) version of the flu virus that can only survive in your nose (the nasal vaccine).
That last one is the only flu vaccine that has an actual virus that can replicate. But it still cannot give you the flu, since the flu is a full-body illness, and the attenuated virus in the nasal spray cannot survive, replicate, or grow in your lungs or other parts of your body. It replicates in your nose, triggers an immune response, and then it’s gone. In rare cases the nasal flu vaccine can give people a mild flu-like illness, but it cannot cause full-blown flu.
I know some folks reading this will swear that they, or someone they know, totally got the flu from the flu shot once. But remember, we tend to misremember and misunderstand our own experiences. You may remember getting sick, figure that was “the flu”, and blame the flu shot you got. You may also have gotten the actual flu, and blamed the shot for giving it to you rather than remembering the shot is only partially effective.
If you got a flu shot, and then came down with a case of the definite actual flu, here’s what may have happened:
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Maybe the shot didn’t work for you, that time. Like we said above, it’s not perfect.
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Maybe you got very mild flu-like symptoms after the shot. This isn’t super common but it happens—and it’s not the actual flu. Remember, flu tends to be pretty long-lasting and severe. A fever or cough that develops as a reaction to the flu shot won’t last more than a day or so.
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Maybe you didn’t get the shot soon enough. You’re not fully protected until two weeks after you get the shot, so it’s possible to catch the flu in the meantime.
Overall, side effects from the flu shot are minimal to nonexistent for most people. If there’s a reason the shot might be risky for you, your doctor or the person who administers your shot will be able to discuss this with you. For example, infants under six months and people with life-threatening allergies to ingredients of the vaccine should not get the shot. It’s recommended for almost everyone else.
Myth: It’s not the right time to get a shot
September might seem too early to get a flu shot, since the disease isn’t really circulating yet. But remember, if you wait to get the shot until everyone you know is getting sick, you might get infected before the vaccine has a chance to take effect.
The CDC says that the best time to get your flu shot is in September or October, so that you’re protected in case flu season starts early, and your protection will last through the months that the flu is most commonly circulating. That’s right now, and there’s no such thing as too late to get a flu shot, as long as pharmacies still have it in stock.
The only real caveat is that getting the flu shot early—in July or August, when pharmacies first get it in stock—may make actually sense for some people:
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People who are in their third trimester of pregnancy during that time should get a shot to protect their baby as well as themselves (some of those antibodies will stay with the baby after birth)
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Children who need two doses should get the first shot in late summer so that they can get the second shot closer to flu season.
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Anybody who might not be able to get their flu shot during September or October should get it whenever they can. Better early (or late) than never.
The rest of us should get the shot as soon as it’s convenient, with a goal of getting it done by Halloween. If you forget, though, and find that everyone around you is getting sick in January, you should still go ahead and get the shot then. It will still protect you for however much of the flu season remains.
Remember the two week delay, though: If everyone around you is sick and you go get your shot after they cough on you, you could get sick anyway, because the shot wasn’t there in time to protect you. That’s why earlier is better. You’re less likely to get sick, and less likely to fall prey to this particular myth.
