Buzz
After getting a flu shot, you might notice some soreness in your upper arm that lasts a day or two. This is a normal reaction, signaling that the vaccine is doing its job, according to immunologists.
The flu vaccine works by introducing an antigen into your body, which is a deactivated or ‘dead’ virus resembling the flu virus. This exposure trains your immune system by priming cells to produce antibodies should the body face the real virus in the future [PDF]. While the inactive virus can’t cause illness, it prepares your immune system to fight off the flu faster and more efficiently.
As your immune system responds to the inactive flu virus in the vaccine, it releases mediators such as histamine, which trigger inflammation. Inflammation is crucial for combating infections and repairing damaged tissues, but it’s also the cause of that soreness. Since the flu shot is injected into your upper arm, the pain and immune response are usually focused in that area.
According to immunologist Richard Zimmerman, about 20% of people experience this type of painful reaction. If you're one of those prone to soreness after a flu shot, there are a few strategies you can use to ease the discomfort. Dr. Juanita Mora from the American Lung Association suggests taking an ibuprofen about two hours before the shot.
“You could also apply ice to the injection site to reduce swelling and redness,” Dr. Mora added.
It’s also helpful to keep your arm moving after receiving the shot, as this prevents the vaccine from becoming too concentrated in one area. Alternatively, you might consider getting the shot in your non-dominant arm to avoid interfering with daily activities due to pain.
But any discomfort is worth it: Even if you’ve never had the flu, there’s still a chance you could catch it. Plus, getting the flu shot helps protect higher-risk groups, like children, seniors, and those with chronic illnesses, who may be unable to get the vaccine themselves. Staying current with vaccinations is one of the easiest ways to support community health.
