The 8 Worst Flu Shot Mistakes According to Immunity Experts—Plus, Here’s Who Needs a Flu Shot in 2023

Updated: Sep. 22, 2023

These flu shot mistakes can reduce the efficacy of that jab. Here’s when to get your flu shot for maximum protection, plus experts' tips to enhance the effectiveness of your shot since experts predict an early flu season this year.


How bad will the 2023-2024 flu season be?

Many people underestimate influenza, but this seasonal virus causes millions of cases and thousands of deaths each year. From October 2022 through April 2023, between 20 million and 54 million Americans contracted influenza—that’s one in every six people, according to the Centers for Disease Control and Prevention (CDC). That’s a fairly normal season, but that was last year. Experts say that while they aren’t necessarily anticipating a terrible flu season for 2023-2024, they are predicting this season may start earlier than normal. 

Linda Yancey, MD, an infectious disease doctor affiliated with Memorial Hermann hospital in Texas, says these predictions aren’t an exact science but do tend to offer a reliable projection.

Dr. Yancey explains that every year in March, the FDA reviews data from the previous flu season, as well as the circulating strains in the southern hemisphere during their winter. Then they estimate what flu season will look like in America.

This year, there are four prevalent strains the FDA has deemed the greatest threats and therefore recommended for inclusion in the 2023-2o24 flu vaccine: Influenza A, H1N1 Victoria/Wisconsin, influenza A H3N2 Darwin, influenza B Victoria, and influenza B Yamagata. This is slightly different from last season’s mix, which can make it more unpredictable.

One way you can protect yourself and your loved ones is to get your flu shot—yes, you: “Simply put, because it works,” Dr. Yancey says. “The flu shot is recommended for everyone. It doesn’t prevent all cases of the flu, but it dramatically decreases the odds of getting a severe case.” (She adds that you should get the new 2023 Covid-19 shot while you’re at it, since most people can get both the flu shot and Covid shot on the same day—and here’s the best arm to get your Covid shot in. After your vaccines, you may want to make your commitments the following day allow time for rest.)

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When should you get your 2023-2024 flu vaccine?

The combo of an earlier start to flu season and different strains means that it’s more important than ever that people get the flu shot as soon as it becomes available, Dr. Yancey says. “Vaccines work best if they are given prior to exposure to the disease,” Dr. Yancey says. “Getting a flu shot early in the season ensures that your immune system will have time to build immunity.” She says this means it’s best to get the flu shot in September or early October for most folks, although it can still help if you get it later.

However, if you’re over the age of 65, you should talk to your doctor about when to get your flu vaccine. In the past, they’ve advised waiting until at least late October to get your vaccine because the protection wanes more quickly in older individuals. If you’re older and get the vaccine too soon, protection might not last the entire flu season. Since this year’s season is predicted to start earlier, your doctor may want you to get it sooner. 

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Why you should get your flu shot

Many vaccines offer near-total protection against a disease, but the flu shot isn’t one of them. The CDC estimates the annual flu shot reduces your risk of catching the flu by 40% to 60%.

If that seems like a safe margin to gamble with, you might want to think again. The flu is a serious illness that can lead to pneumonia, hospitalizations, and death, says Margaret Khoury, MD, pediatric infectious disease doctor and regional lead of the Kaiser Permanente Southern California Flu Vaccination Program.

The CDC spells it out like this: During the 2019-2020 flu season, flu shots prevented 7.5 million illnesses, 3.7 million medical visits, 105,000 hospitalizations, and 6,300 deaths. Notably, the flu shot offers critical protection for children—the CDC says 80% of kids who die from influenza are unvaccinated.

While the only real way to mess up your flu shot is not to get it at all, top experts tell The Healthy @Reader’s Digest the biggest mistakes people make when it comes to the flu vaccine.

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woman doctor giving an elderly man a shot
iStock/Catherine Yeulet

Flu shot mistake #1: Not getting the vaccine because you think you’re too old—or young

Anyone older than six months should get the flu vaccine (unless you have a medical reason to avoid it, like an allergy or an immune disorder), Dr. Khoury says, adding that this is especially important for the following groups:

  • children older than six months or anyone who cares for children
  • the elderly or their caregivers
  • pregnant women
  • people with asthma, heart disease, or diabetes
  • anyone over age 50
  • anyone who suffers from an autoimmune disease
  • anyone who lives in a nursing home or long-term care facility
  • those with obesity
  • all healthcare workers

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African American doctor giving a man his flu shot
iStock/Steve Debenport

Flu shot mistake #2: Skipping this year’s flu shot because you got one last year

Every year, influenza viruses mutate, which means the virus isn’t the same as the one you were vaccinated against last year. “People need to get the flu shot every year because flu viruses are constantly changing, and it is not unusual for new flu viruses to appear each year,” says Caroline Sullivan, nurse practitioner, primary care provider, and assistant professor at Columbia University’s school of nursing in New York City. Plus, Sullivan says, “Studies have shown that the body’s immunity to influenza, either through natural infection or vaccination, declines over time.”

As we referenced above, here’s how each year’s flu vaccine works: Ahead of each flu season, health experts around the world determine which flu strains pose the greatest threat. This research informs what goes into that year’s flu shot—exactly how effective it is depends on the accuracy of those predictions, with some years faring better than others. The final product is either a “trivalent” or “quadrivalent” flu shot, which means it protects against the three or four strains of influenza. So, even if experts only get one or two strains correct it’s still worthwhile to get the shot, Dr. Khoury explains.

And if you got the vaccine last year and still came down with the flu, it’s natural to question getting the flu shot again. But experts say that in these scenarios, the virus has mutated so the vaccine hasn’t kept up, or the illness you might have had was not true influenza, but another virus altogether.

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Asian woman sneezing into a tissue

Flu shot mistake #3: Avoiding the vaccine because you suspect you already got the flu

Are you sure it was the flu and not some other recent virus? Not only can you not be sure you’ve had it (unless you were tested), but there are multiple strains of influenza circulating every year—so getting one strain doesn’t protect you from the others, Dr. Khoury says.

As a bonus, even if you are sick, the flu shot can lessen the severity of your illness and protect you from other viruses through cross-protection antibodies, she says. These are viruses that are similar to the strains of flu in the flu vaccine, which your body learns to fight off.

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woman outdoors holding her arm

Flu shot mistake #4: You believe the flu vaccine will actually give you the flu

Our experts say this is the most common misconception people have about the flu shotbut science doesn’t back it up. Dr. Khoury says the flu shot is made in such a way that it either contains no flu virus at all, or an inactivated or noninfectious virus. So while the flu vaccine may cause a low-grade fever and muscle aches in some people, these symptoms are usually temporary and are not actually an influenza infection.

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African American young man looking warily at a syringe in a doctor's hands

Flu shot mistake #5: You make the flu vaccine hurt even more than it should by tensing up

Fear of needles is a very common reason people avoid the flu shot, and there are ways to help you deal with this, says Amy Baxter, MD, founder and CEO of MMJ Labs. “I do the scientific research on why, but the important thing is once someone is afraid, they tend to keep that fear for life,” she says.

Fortunately, you can have some control over how painful the vaccination experience is for you. “Tensing a muscle makes it hurt more, so try to relax the arm and focus on breathing,” says Baxter. “There are many strategies to reduce needle fear, but it usually takes three good experiences to help someone overcome it.”

Learn how one woman overcame her fear of needles for good

people doing deadlifts at a gym

Flu shot mistake #6: You don’t move your body immediately after your flu shot

A 2022 study published in the peer-reviewed scientific journal, Brain, Behavior, and Immunity, found that light to moderate exercise—like walking or jogging—30 minutes after you get your flu shot helps your body churn out more flu-fighting antibodies. (The study also shows that this is true for the COVID-19 vaccine—and that exercise doesn’t increase the vaccine’s side effects.)

What’s more, the enhanced immune response from just that one workout lasts for weeks beyond your vaccination. 

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doctor discussing treatment with a patient

Flu shot mistake #7: You wait too long to get the vaccine

A typical flu season in North America starts as early as October and continues into May—and the flu shot works best early in the season, Dr. Khoury says. The sooner a person is vaccinated, the more antibodies and immunity they can develop before the height of flu season, which is January and February, she explains.

And since it takes about two weeks to build up immunity after you receive the vaccine, the CDC recommends getting the flu shot as soon as it is available (which is why most doctor’s offices and pharmacies start offering it as early as September).

But if you find yourself unvaccinated in late January or February, it’s still recommended to get the flu vaccine—better late than never.

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pregnant woman holding a teddy bear

Flu shot mistake #8: You don’t get the flu vaccine because you’re pregnant or breastfeeding

This is an understandable question among pregnant and breastfeeding women, as well as those trying to conceive, but from the CDC and our immunity experts, the verdict is in: You should absolutely get vaccinated. “Pregnant women should definitely get a flu vaccine, as they’re one of the most susceptible populations and can become seriously ill and even die from the flu,” says Laura Haynes, PhD, a professor in the department of immunology at the University of Connecticut. This is just one reason parents need to stay updated on all their vaccines.

Plus, if you’re breastfeeding an infant and have received the vaccine during your pregnancy, then you pass the immunity you acquired from the vaccine onto your newborn or infant—this is called “passive immunity,” and it’s a benefit of breastfeeding, she explains. Also read: Which Vaccines Do You Need in 2023-24? Here Are Experts’ Recommendations for All Ages

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Additional writing and reporting by Charlotte Hilton Andersen.