Side effects of the flu vaccine 2022

Soreness/redness/swelling/bruising at the injection site may occur and may last for up to 1-2 days. Fever, muscle aches, headache or weakness may also occur. If any of these effects continue beyond 2 days or become bothersome, tell your health care professional.

Rarely, some people have symptoms such as fainting, dizziness, vision changes, or ringing in the ears just after getting a vaccine injection. Tell your health care professional right away if you have any of these symptoms. Sitting or lying down may help, since these symptoms usually don't last long.

Remember that this medication has been prescribed because your health care professional has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your health care professional right away if you have any serious side effects, including: mental/mood changes, numbness/tingling, seizures.

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, severe dizziness, itching/swelling (especially of the face/tongue/throat), trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your health care professional.

Contact the health care professional for medical advice about side effects. The following numbers do not provide medical advice, but in the US you may report side effects to the Vaccine Adverse Event Reporting System (VAERS) at 1-800-822-7967. In Canada, you may call the Vaccine Safety Section at Public Health Agency of Canada at 1-866-844-0018.

Friendly reminder: It’s time to get your annual flu vaccine if you haven’t already. Flu season is already ramping up, and experts are expecting an especially rough fall and winter, so getting your shot before the end of October is pretty darn important. There are plenty of precautions that can help protect you from the flu—washing your hands frequently and masking up, to name a couple—but the vaccine is a tool that should top your list.

Like any vaccine though, the flu shot does come with potential side effects—and this is usually a good thing. It’s a strong sign that your immune system is responding to the vaccine and building up those all-important, infection-fighting antibodies, as SELF previously reported.

But how long do flu shot side effects last? Here’s what you should know so you can plan ahead, just in case you do end up feeling a bit crummy after your appointment.

How long do flu shot side effects last for most people?

First it’s important to note that everyone reacts differently post-vaccine. Some people get the flu shot and feel totally fine, while others may feel a bit unwell. According to the Centers for Disease Control and Prevention (CDC), the most common side effects that can occur include soreness, inflammation, or swelling in the arm or around the injection site; low-grade headache; fever; nausea; muscles aches; fatigue; and fainting (especially if needles tend to freak you out).

“Most people get pain at the injection site and a sore arm,” John Sellick, DO, infectious disease expert and epidemiological researcher at the University at Buffalo/SUNY in New York, tells SELF. “It’s typical of what we see with most other vaccines.”

Thankfully these symptoms are usually mild and go away on their own. The duration “varies from person to person” but, in general, side effects from the flu vaccine “usually last about a day”—again, if you have them at all, infectious disease expert Amesh A. Adalja, MD, a senior scholar at the Johns Hopkins Center for Health Security, tells SELF. 

How to feel a bit better when side effects strike

Again, any discomfort post-vaccine should be pretty short-lived, Dr. Adalja says. But if you’re not feeling great, there are a few things you can do to try to speed up your recovery time:

• Take OTC pain relievers. Acetaminophen is a good option for reducing fever and easing any soreness, Dr. Schaffner says.
• Move your affected arm. This can help promote blood flow to the area, which helps repair the muscle in your arm that’s (very slightly) torn from the injection, Dr. Schaffner says.
• Cool it down. Putting a cool, damp washcloth over your arm can help with any swelling and visible inflammation or reddening of the skin, Dr. Schaffner says.
• Drink plenty of fluids. Being hydrated won’t necessarily get rid of the side effects, but it enables your body to work more efficiently, Dr. Sellick says. Also, being dehydrated can make you feel even worse.
• Rest! If your body feels off and you’re just sluggish, take it easy, Dr. Schaffner says. Consider going to bed a bit earlier, or doing lighter stretching instead of an intense run, for example.

When should you talk to a doctor about potential flu shot side effects?

Some people may have an allergic reaction to a component in the flu vaccine, like egg protein, but this is fairly rare. If you do have an allergic reaction, it usually happens within a few minutes to a few hours after you get the shot, the CDC says, so you’ll know pretty quickly; those who are allergic can potentially experience trouble breathing, wheezing, hives, weakness, a rapid heartbeat, and/or dizziness. You should always let your health care provider or pharmacist know in advance if you have a history of allergies or severe reactions to any vaccines, so you can talk through your options with that in mind.

And, you probably already know this, but it never hurts to mention it again: The flu shot does not actually give you the flu—even if it kinda feels like it for a day. “It’s absolutely medically impossible to get the flu from the flu vaccine,” Dr. Schaffner stresses.

If you suddenly start experiencing respiratory symptoms after you get your vaccine—like coughing, sneezing, or a sore throat—Dr. Sellick says that’s a sign you probably caught something before your appointment. It’s totally possible to come down with a cold, the flu, or even COVID before you get vaccinated, and then coincidentally develop symptoms of that illness shortly after you get your jab.

“Some people may get their flu shot on Monday and start to have a runny nose or sore throat on Tuesday,” Dr. Schaffner explains. That usually “means you picked up a virus from somewhere else.” 

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