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Why does your arm hurt after vaccination?

Immunizations can cause soreness where you got the shot, and most of the time that’s normal

No one enjoys getting a vaccination: the needle poke, the sting of the medication, the resulting soreness for the next few days. Of course, most people know that immunizations help protect against illnesses and diseases, and are necessary for our health. In other words, they’re worth a little discomfort. 

You may be wondering why your arm hurts after a shot and if it’s normal. You may also ask yourself if you should get further vaccines if you have a reaction. Here’s what the science says.

Sore arm after vaccine? That’s normal.

Side effects after receiving a vaccination are normal and aren’t necessarily cause for concern. Mild injection site pain and irritation (also known as a sore arm) are common after receiving many vaccinations, including the COVID-19 vaccine. In fact, about 65% to 82% of people will have injection site pain with the COVID vaccine, and more specifically, if you’ve gotten the Moderna shot. 

The COVID vaccine, along with many vaccines in general, can cause common side effects to occur such as:

  • Redness or soreness at the site of injection
  • Muscle aches
  • Fatigue
  • Fever or chills
  • Headache

“Arm pain is likely to begin within 24 hours of vaccination and lasts a few days after the vaccine is administered,” says Grant Anderson, Ph.D., an associate professor in the University of Minnesota College of Pharmacy. A sore arm after a COVID shot is the most common side effect, and according to Anderson, only 25% of vaccinated people report experiencing side effects other than arm pain.

Some vaccines can hurt more than others. Along with the COVID vaccine, the shingles vaccine, Shingrix, can cause more and longer-lasting pain than other vaccines. The flu vaccine, on the other hand, usually causes less pain, explains Anderson.

RELATED: Can you get the flu from the flu shot?

Serious vaccine side effects

A more serious reaction to vaccines is rare and isn’t always cause to not receive any more vaccinations in the future. For the most part, reactions are mild and go away in a few days. But there are some instances where you should contact your healthcare provider for medical advice. 

Some side effects that are more serious include:

  • Shoulder pain: This occurs when you receive the shot too high on your upper arm. This can cause pain that starts within 48 hours along with difficulty moving your shoulder around. It lasts longer than the normal timeline for injection site reaction for that vaccine and taking pain medication doesn’t relieve the pain. 
  • Infection: It’s rare, but receiving a shot punctures your skin, and does put you at a very small chance of the area becoming infected. If this occurs, it’s likely you would need to be treated with antibiotics.
  • Anaphylaxis: The risk of a serious allergic reaction is about 1.31 for every million vaccine doses. Symptoms of anaphylaxis include swelling of the face, lips, and neck along with rapid heartbeat, and trouble breathing. It usually happens immediately after and in lesser cases, several hours post-vaccination. Very few people will have an anaphylactic reaction after 24 hours. 

Arm pain is inconvenient, but it should go away after a day or two. Try to move your arm around throughout the day and use cold compresses, suggests Vino Palli, MD, founder of MiDoctor Urgent Care in New York City. If you’re still having arm pain weeks after vaccination, or have concerns, call your healthcare provider who can determine whether you need medical attention. 

What is COVID arm?

You may have heard of COVID arm and are concerned it will happen to you. This reaction doesn’t happen to many people and usually resolves on its own, even if it’s not fun to experience. COVID arm is a local reaction by your immune system, meaning it occurs around the injection site. You may experience:

  • A painful and/or itchy rash that can get very large
  • Swelling
  • Warmth
  • A firm bump under your skin where you received your shot

According to the Centers for Disease Control and Prevention (CDC), COVID arm can start a few days to a week or more after getting your shot. It’s not caused by the coronavirus itself, since both the Moderna and Pfizer vaccines are MRNA vaccines that don’t contain the virus.

According to Phase 3 trial results in the New England Journal of Medicine, this rash affected 0.8% of participants after the first dose, and 0.2% of participants after the second shot. In both cases, a very small number.

“It’s not completely known why this occurs, but it’s considered rare and shouldn’t be a reason to put off getting the vaccine,” Dr. Palli explains. The immune response to the vaccine is thought to come from the muscle as it absorbs the vaccine. Your body’s immune system thinks the SARS-CoV-2 spike protein produced by the vaccine is in fact a virus. The immune system then mounts a defense, only this defense goes overboard and causes a bigger reaction than what is considered normal. It’s similar to an anaphylactic reaction, but instead of affecting the entire body, this hypersensitivity is contained around the injection site only. The Shingles vaccine behaves similarly. People who receive it could get a rash as well. 

Age can play a role in who has a higher chance of having COVID arm. “It seems as if younger patients have more arm pain compared to older patients looking at a study that was done using the Pfizer vaccine,” Dr. Palli says.

If you do notice a rash after your first COVID-19 vaccination, inform your healthcare provider before you get the second one. A rash may not be a reason you shouldn’t get your second dose. However, your healthcare provider may advise you to get the second injection in your other arm. Other things that can help treat the rash include:

  • Topical steroid medications for the itching, such as OTC hydrocortisone cream
  • Topical anesthetics such as lidocaine
  • Avoiding fabric over the injection site to prevent further skin irritation

RELATED: Compare COVID vaccines

Are side effects worse after the second COVID vaccine?

“For many recipients, side effects are worse after the second dose,” says Anderson. Local inflammation from the body’s inflammatory response leads to redness, warmth, swelling, and pain at the injection site.

“When enough of these substances are released, muscle aches can occur and you begin to feel tired,” Anderson explains, “With the second dose, your immune system is really fired up and ready to immediately and forcefully respond to the vaccine components.” However, he adds, this is a good sign your body is mounting a strong immune response. And if you don’t have any side effects from the vaccine, it doesn’t mean the vaccine didn’t work or that you have a weak immune system. “The protective immunity afforded by the vaccines takes longer to develop and isn’t associated with these side effects,” Anderson says.

How to treat a sore arm after vaccination

Although a sore arm after COVID shots is temporary, there are a few things you can do at home to help treat a sore arm after your vaccine: 

  • Use a cold compress on the injection site
  • Move your arm around frequently throughout the day
  • Take over-the-counter (OTC) pain medications, such as Advil (ibuprofen) and Tylenol (acetaminophen) if approved by your provider 
  • Use antihistamines such as Benadryl if you experience itchiness

Unless you have a health condition that prevents you from taking certain OTC pain relievers, such as a bleeding condition or liver or kidney problems, you may find relief from arm soreness as well as certain other vaccine side effects such as headache or fatigue. 

However, you want to avoid taking OTC pain medications before your vaccine in anticipation of side effects. While it may decrease your arm soreness, “the local inflammation is beneficial to the development of a vigorous immune response and anti-inflammatory drugs may reduce this beneficial response,” Dr. Anderson explains. 

Preventing arm pain after vaccines

There are a few other ways to try to prevent arm pain when you’re about to get your shot: 

  • Request the vaccine goes in your non-dominant arm. This may help as you won’t use it as frequently as your dominant arm and may not notice the soreness as much. 
  • Relax your arm before your shot. Injections into clenched muscles can cause more pain.
  • You may be able to request ice or a numbing spray before your vaccination.

Although getting a vaccination isn’t usually comfortable, it’s important to know that arm soreness is normal and usually goes away within a few days. If you have any questions and concerns about vaccines and their side effects, talk with your healthcare provider to get the best medical advice for you.