Like with any vaccine, there is a risk of developing side effects with the flu shot. Most side effects are mild and at the injection site. Stomach upset is not very common, but is possible.
Every year, health experts recommend everyone who’s able to get an annual influenza vaccine. Most people get this vaccine via a flu shot in the arm.
The flu shot is designed to help protect against the
Any side effects from these vaccines are caused by your immune system activating, which starts building protection in your body against influenza. Every body is different, so not everyone will have side effects, and when they do, side effects can vary.
Here’s what you need to know about the likelihood of an upset stomach after getting an annual flu shot, other possible side effects, and what you can do about them.
Stomach pain is a possible side effect of a flu shot, though how often it happens is unclear.
Like other side effects, stomach pain or upset should resolve within a
According to the
But while the authors note that the vaccine likely decreased the rate of such symptoms, more research is needed to determine how many people experience diarrhea as a side effect of the flu shot itself.
Other GI side effects from a flu shot are possible, but they’re still not common.
- inflammation of the small intestine and colon (enterocolitis)
- the “stomach flu” (gastroenteritis)
- inflammation of the pancreas (pancreatitis)
- gastrointestinal infections
However, the researchers note that it’s not clear whether such GI side effects are linked to the flu shot or if they developed for other reasons. These GI side effects were also not very common. More targeted research is needed to determine cause and effect.
Aside from an upset stomach and GI side effects, there are other short-term and long-term side effects of the flu shot:
Short-term side effects of flu vaccine
The flu shot’s short-term side effects include:
- injection site reactions, such as redness, soreness, or swelling
- body aches
Like other flu vaccine side effects, these are usually mild and will resolve after a
Long-term side effects of flu vaccine
While rare, severe and life threatening allergic reactions are possible after receiving the flu vaccine. These may be attributed to allergies to some of the vaccine ingredients, such as gelatin or egg protein.
Another possible but rare complication is developing Guillain-Barré syndrome. However, this only occurs in about
The side effects of the flu vaccine are similar in babies as in other age groups. Babies may also experience a decreased appetite, tiredness, and fussiness after getting the flu vaccine.
You can help ease an upset stomach by:
Get medical help right away if you’re experiencing possible symptoms of an allergic reaction to the flu shot. Symptoms of a severe reaction may develop
within minutes or a few hoursafter getting the vaccine and may include:
- difficulty breathing
- increased heart rate
- pale skin
You may also want to reach out to a doctor if you’re having flu shot side effects that last longer than a few days.
You should be able to resume your usual activities after getting a flu shot. If you do experience side effects, you may want to try some of the following:
- Take over-the-counter pain relievers for arm pain, fever, or muscle aches. These include acetaminophen (Tylenol) or ibuprofen (Advil) 2 hours before your scheduled flu shot. However, aspirin is not recommended for people under age 18.
- Get plenty of rest.
- Drink plenty of water to help prevent dehydration.
- Stay warm with blankets or by wearing layers.
This is also particularly important if you have a
You also have a higher risk if you have any of the following conditions:
- chronic lung disease, such as asthma or COPD
- kidney disease
- heart disease
- a history of stroke
- metabolic disorders
Who should avoid it
On the flip side, the
- infants under 6 months of age
- people with severe allergies to gelatin or other ingredients in a flu shot
- anyone with a history of a severe reaction to a flu vaccine
- people who are currently ill
- those with a history of Guillain-Barré syndrome (you can ask a doctor first)
A stomachache and other GI ailments are uncommon but possible side effects from the flu shot. Like other flu vaccine side effects, they are usually temporary and should go away on their own.
Speak with a doctor if any stomach upset or other side effects last longer than a few days.