11 Totally Normal Side Effects of the Flu Shot, According to Doctors
The flu shot can’t make you sick, but it does come with the potential of flu shot side effects, just like any other vaccine or medicine.
In most cases, this translates to a sore arm but there’s even a chance you won’t experience that. “The majority of patients really don’t have any side effects,” says Sandra Kemmerly, M.D., system medical director for hospital quality at Ochsner Health System in New Orleans. And when symptoms do occur, they’re usually mild and clear up in a day or two, she says.
Basically, flu shot side effects are not something to stress over. Instead, you should be concerned about what could happen if you don’t get your flu shot, like the risk of getting seriously ill from influenza.
Still, knowledge is power and it makes sense to want to know what you could (potentially) be in for. Here are the most common side effects of the flu, for the just in case.
What are the side effects of the flu vaccine?
Whether you get a flu shot or the spray-mist type, side effects are generally no big deal. You may experience the following:
✔️Soreness or aching in your arm
Your arm might be sore or uncomfortable after getting the shot, but this is a good thing: It means your immune system is responding to the vaccine and creating antibodies, says Dr. Kemmerly. Plus, it’s usually “one day of discomfort,” says Claudia Vicetti, M.D., a pediatric infectious disease specialist with UnityPoint Health in Cedar Falls, IA. She adds, “and not everybody gets that [side effect].”
✔️Redness, pain, or swelling at the injection site
This is another good sign that your immune system is raring to go and responding to the vaccine properly, Dr. Kemmerly says. Plus, any time something breaks the skin barrier (like a needle), it may get red and swollen as your body reacts to it as a foreign object. This side effects is common and should only last a few days.
✔️Low-grade fever
Experiencing a low-grade fever (below 101 degrees) after the flu shot is possible, but it’s not very common. If it’s any higher than that, you may already be sick with another virus that commonly circulates during flu season. A person might catch a cold, for example, or RSV (respiratory syncytial virus, a common childhood illness).
Oftentimes, people delay getting a flu shot until flu season is in full swing, Dr. Kemmerly points out. They were already “incubating” the flu virus and “then, lo and behold, they got the flu—but totally unrelated to the flu shot,” she says.
✔️Nausea, headaches, or fatigue
These are all totally normal reactions as your body responds to the flu vaccine, the CDC says.
✔️Dizziness or fainting
Like any other vaccine, some people may experience dizziness or fainting after getting a flu shot, but this has much more to do with the process—getting a needle poked into your arm—than the vaccine itself, the CDC says. The organization emphasizes that nearly all vaccines receive reports of people fainting afterward, so it’s not unique to the flu shot alone.
✔️Coughing or sneezing
The nasal flu vaccine, the type your child might get if he or she doesn’t have asthma or a recent history of wheezing, can cause some of the same side effects as the flu shot—minus the sore arm—plus some additional ones. “There can be some coughing and sneezing,” Dr. Kemmerly notes, “but for the most part people feel pretty good.”
✔️Sore throat
While the flu shot is unlikely to give you a sore throat, the CDC says that you may experience this side effect with the nasal flu vaccine. If you happen to experience this side effect, it will usually happen soon after you get vaccinated and be mild and short-lived.
✔️Guillan-Barré syndrome
Guillain-Barré syndrome (GBS) is a neurologic condition that attacks your body’s nerve cells, in turn causing muscle weakness or paralysis in severe cases. It got attention earlier this year after the Food and Drug Administration (FDA) shared that there is an “observed increased risk” of the condition after people were vaccinated with the Johnson & Johnson COVID-19 vaccine. Based on an analysis of Vaccine Adverse Event Reporting (VAERS) data, there were 100 preliminary reports of GBS after 12.5 million doses were given of the Johnson & Johnson vaccine, the FDA said. Of those, 95 were serious and required hospitalization, and one person died.
But that was for the COVID-19 vaccine—not the flu vaccine. There are people who do develop serious side effects after getting the flu vaccine, including GBS. (These people fall on the list of people who should not get a flu shot.) The condition is extremely rare. In fact, for every 1 million flu shots given, only one or two of those people will develop GBS, the CDC states. Each year, an estimated 3,000 to 6,000 people develop GBS of any cause in the U.S.
✔️Allergic reactions
There are people who may experience an allergic reaction to the flu vaccine or its components, such as gelatin, antibiotics, or other ingredients. The CDC says that signs of a severe allergic reaction can include difficulty breathing, wheezing, swelling around the eyes or lips, hives, high fever, and a fast heartbeat.
Life-threatening reactions to the flu shot are extremely rare. “I’ve been practicing for 30 years. I’ve never seen an anaphylactic reaction to the flu shot,” says Dr. Kemmerly. Dr. Finkel agrees that life-threatening allergic reactions to flu shots are “very rare,” but it’s still possible to have an allergic reaction to an ingredient in the vaccine. “Signs of serious allergic reaction can include breathing problems, hoarseness or wheezing, hives, paleness, weakness, a fast heartbeat, or dizziness,” Dr. Finkel says. “If they do occur, it is usually within a few minutes to a few hours after receiving the shot.” (If you happen to have any of those symptoms, seek medical care ASAP, she says.)
⚠️ If you’ve had a life-threatening allergic reaction to the flu shot in the past, you should not get the vaccine.
If you have an egg allergy, you can still get vaccinated, the CDC says, but it should be done in a controlled setting where you can be monitored. In this case, talk to your doctor about your egg allergy so you can both make an informed decision about your vaccine.
Why do some people feel sick after the flu shot while others don’t?
Doctors say reactions to the flu vaccine differ from person to person and that multiple factors are likely at play.
Think about how people respond to the common cold. Some folks get a runny nose and go on with their lives, while others stay home with a fever or develop a cough. It’s the same with the flu shot, says Dr. Vicetti. “You’re stimulating your body, and your immune system may react in different ways,” she says.
“The flu” isn’t a single virus. Each season, a new vaccine is developed to match circulating strains. Getting a flu vaccine can protect you against the same or related viruses in the vaccine, but it won’t cover every possible strain that a person might encounter, the CDC explains. This year’s vaccine will target the following strains:
an A/Victoria/2570/2019 (H1N1)pdm09-like virus;
an A/Darwin/9/2021 (H3N2)-like virus;
a B/Austria/1359417/2021-like virus (B/Victoria lineage)
a B/Phuket/3073/2013-like virus (B/Yamagata lineage)
Even though it is not 100% effective, getting a flu shot is the best way to protect yourself from getting sick, and can significantly lower your chances of winding up in the hospital. It is important to get vaccinated before the end of October, so your body has time to build up immunity.
Once you do get the vaccine, you may be one of the rare few that feels a bit crummy afterward, but it shouldn’t last very long. Here are the flu shot side effects to know, when you should and shouldn’t worry, and how to feel better once side effects hit.
How long do flu shot side effects last?
It really depends. Typically “they last a few hours to a few days,” says Diana Finkel, D.O., an associate professor of infectious diseases at Rutgers New Jersey Medical School.
Still, “duration varies from person to person,” says infectious disease expert Amesh A. Adalja, M.D., senior scholar at the Johns Hopkins Center for Health Security.. Just know this, per Dr. Adalja: “If side effects persist for several days and are more than just injection site pain and slight achiness, there may be another illness present.”
When should I get the flu shot?
The CDC and public health officials generally recommend that you try to get your flu shot before Halloween. But, if you can’t make that deadline, Dr. Adalja says it’s best to just get it as soon as you can.
Flu activity is already jumping up across the country, so this is definitely something you want to do sooner rather than later.
How to treat flu shot side effects
Again, flu shot side effects are usually minor, if you have them at all. But if you’re uncomfortable, try these self-care measures to feel better ASAP:
For muscle aches, headache, or flu-like symptoms, take a pain reliever, such as Tylenol or ibuprofen.
For arm pain after the flu shot, apply a cool compress.
The same goes for side effects of the nasal flu vaccine. Treatment is based on a person’s symptoms, Dr. Kemmerly says. All in all, minor aches are a small price to pay for the vast protection the flu vaccine provides for both you and those around you.
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