Flu Vaccine Side Effects: Common and Rare – Health.com

It's important for everyone 6 months old and older to get vaccinated against influenza (the flu) yearly. The flu infected as many as 31 million people in the U.S. during the 2022-2023 flu season. The flu vaccine is highly effective and safe but may cause mild side effects like pain, swelling, or redness where the shot was given. These side effects typically go away within a few days.

Other side effects can include aches and pains, dizziness, and mild fever. You can typically relieve flu shot side effects using a pain reliever. Read on to learn about the common flu vaccine side effects and when to get vaccinated.

Flu shots have been around since the 1930s and are considered extremely safe and effective. Most side effects of the flu vaccine are mild and go away within a few days.

All vaccines can cause side effects, and most of these symptoms are entirely normal. Side effects are basically telling you that your immune system is working. The immune cells are rushing to where the vaccine was injected to react to it.

The standard-dose flu shot for people ages 6 months to 64 years old contains an inactivated (killed) flu virus. The most common side effects from this vaccine include pain, swelling, or redness where the shot was given. Other side effects can include aches and pains, dizziness, and mild fever.

These side effects can occur from any injected vaccine, meaning your immune system has been activated. Not having these side effects doesn't mean your immune system isn't responding to the shot. Reactions vary from person to person.

There's always a small percentage of people who have a headache and muscle aches or pains the next day. These aches and pains typically develop on the day you receive the flu shot and go away a few days after.

Taking a pain reliever, such as Advil (ibuprofen) or Tylenol (acetaminophen), can ease discomfort. Some evidence suggests that pain relievers may impact how your body responds to the flu vaccine. Keep in mind that the data is inconclusive, and it's not clear whether you can't take pain relievers.

Some people can feel dizzy or faint after getting a flu vaccine. Talk to a healthcare provider before they administer the vaccine. They may recommend that you have a snack or sit down after you receive the vaccine.

You may develop a mild fever after getting a flu shot, but it's uncommon to have a high fever. A fever typically goes away within a few days and can be treated with Advil or Tylenol.

Almost everybody gets a sore arm after getting a flu shot. You might also notice redness, swelling, and warmth at the injection site. These side effects are usually gone after a few hours, but some people still have them the next day or two. Taking Advil or Tylenol can treat an injection site reaction.

Severe side effects from the flu vaccine are very rare. However, some people can develop an uncommon neurological disease called Guillain-Barr syndrome (GBS) or a severe allergic reaction.

One rare side effect is GBS, which is a neurological disease that causes muscle weakness and paralysis. These symptoms, which typically worsen within a few hours, involve both sides of the body. You might require breathing assistance if GBS affects the nerves of the chest and diaphragm, or the muscle under the lungs.

Other GBS symptoms include:

GBS develops after one or two out of every million vaccine doses. Some evidence suggests that the risk of GBS is actually higher after getting the flu than it is from getting the vaccine.

Severe allergic reactions are extremely rare, affecting fewer than one or two in one million people. Signs of a severe allergic reaction can include:

These symptoms generally develop within hours of receiving the vaccine. Call 911 or contact a healthcare provider right away any time someone experiences such symptoms.

Several different kinds of flu vaccines are offered each year. What vaccine you get depends greatly on your age and other factors, such as health conditions and allergies.

The vaccine may be given by injection or nasal spray. Special dosages are available for the youngest and oldest recipients. The vaccine can also be made using an inactivated (killed) virus or an attenuated (weakened but live) virus.

Not all flu vaccines are made the same way or intended for the same people, even though they offer the same protection. The side effects of flu shots may also be slightly different.

Two different vaccines are made specifically for people aged 65 and older. One shot contains the exact same dose of antigen as the injection for younger adults with the addition of an adjuvant. The other shot is a high-dose version of the vaccine, with four times the amount of antigen.

An antigen is the part of the virus that triggers the immune response. An adjuvant is an ingredient added to help spark a stronger immune response.

The common side effects are the same for all inactivated flu vaccines, regardless of the vaccine: sore arm, perhaps some muscle pain, or a mild fever. All injectables have similar side effects. The rare serious side effects are also the same.

The nasal spray vaccine is available for non-pregnant people aged 2 to 49 who don't have serious, underlying illnesses. It's primarily used in children, but some adults decide they'd rather skip the needle if they can.

This vaccine isn't just an inhaled version of the injectable. It contains a weakened, not killed, version of the flu virus to stimulate the immune system. The nasal spray vaccine doesn't cause the flu since the virus is specially engineered not to multiply once it's exposed to slightly higher temperatures inside the body.

The most common side effects include:

Children may also experience wheezing, vomiting, muscle aches, sore throat, and low-grade fever. These side effects are typically mild and don't last long after vaccination.

Most flu vaccines are made using eggs to grow the vaccine cells. Experts advise that people who have had allergic reactions to eggs receive a flu vaccine under the watch of a healthcare provider who can detect and handle severe allergic reactions.

People who have had severe allergic reactions to egg-based flu vaccines are advised against receiving them in the future. You can likely still receive one of the two flu vaccines that are not made using eggs. It's still important to receive the vaccines under the supervision of a healthcare provider. They can discern and manage severe allergic reactions.

The Centers for Disease Control and Prevention (CDC) advises getting a flu vaccine in September or October to prepare for flu season. The vaccine can still protect you if you get it after October. A flu shot is effective for one year, so it's important to get a new one before each flu season.

Some people may need to get a flu shot early, like in July or August, such as:

Getting a flu shot can mean you have to endure an achy arm for a few hours. Some people may also experience side effects like headaches, nausea, and mild fever. Severe side effects, including GBS and severe allergic reactions, are rare.

The side effects of flu shots are mild and fleeting for most people. The risk of these side effects generally outweighs a case of the flu, which can lead to serious complications. Talk to a healthcare provider if you meet the criteria for a high-dose vaccine, nasal spray, or egg-free option. They can help determine what vaccine to get and when.

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Flu Vaccine Side Effects: Common and Rare - Health.com