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Why Do Flu Shots Make You Sore?

PSA: Being Sore From a Flu Shot Is Your Body's Way of Telling You It's Working

A doctor is giving a vaccine to a young woman on a white background

Like with most vaccines, you can expect to feel a little soreness or tenderness after receiving your flu shot. While the pain can be a bit bothersome, it is temporary and shouldn't prevent you from visiting your doctor's office or local pharmacy to get your shot. If you haven't made a point to get your flu shot yet (here's a friendly reminder!), there are a few minor things you can do before and after to reduce soreness and inflammation.

First off, it's key to note that arm soreness is a positive reaction. It means the shot is working! "When your body's immune system is introduced to the influenza vaccine, it responds by mounting an inflammatory response, which is why you might feel a little sore," Kristamarie Collman, MD, a board-certified family medicine physician in Florida, told POPSUGAR. "This indicates that our immune system is making influenza-fighting antibodies to the vaccine." If exposed to the virus, these antibodies will help fight off the bug.

Additionally, Patricia Egwuatu, DO, a board-certified family medicine physician in Washington, explained another direct cause for soreness or tenderness is due to the injection location site. "The flu shot is usually injected into a muscle, and if the needle is specifically inserted into the deltoid muscle, this can sometimes cause shoulder bursitis," she said.

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One of the most effective ways to avoid discomfort is by moving around the injected arm to help circulate blood flow to the area. Soreness and redness for a day or two is normal and can be treated with a cool compress such as an ice pack. To prevent interference with day-to-day activities such as writing, Dr. Collman recommends getting the vaccine in your nondominant arm. If you know you're susceptible to soreness after the vaccine, it may help to take an anti-inflammatory medication one to two hours prior as a preventive, she said.

For persisting pain, Dr. Egwuatu advises contacting your primary-care physician immediately. Given how flu season and the COVID-19 pandemic are overlapping with one another, now more than ever, it is crucial for you to get a flu shot. Fighting through a day of being sore is better than being stuck several days in bed with the flu, or worse.

Image Source: Getty / Karl Tapales
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