Why does your arm hurt after vaccination?

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.

Why does your arm hurt after a shot?

A sore arm after a vaccine is a normal reaction to an immunization. Mild injection site pain and irritation (also known as a sore arm) are common after receiving many vaccinations, including the influenza vaccine, pneumococcal vaccine, varicella vaccine, and COVID-19 vaccine.

Side effects after receiving a vaccination are normal and aren’t necessarily cause for concern,  such as:

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

Some vaccines can hurt more than others. 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. 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 Grant Anderson, Ph.D., an associate professor in the University of Minnesota College of Pharmacy.

But why does injection site pain occur? Getting vaccinated causes an inflammatory process in the body, says Mykale Elbe, DNP, APRN, a board-certified family nurse practitioner and Director of the MSN Nurse Practitioner Program at Maryville University in St. Louis, Missouri. This can happen after any type of injection as the body responds to the external fluid being injected into the tissue/muscle, Dr. Elbe says.

Usually, injection site pain will occur within the first 30 minutes of receiving any vaccination, including the Shingrix vaccine, says Dr. Elbe. Patients are typically asked to remain at the location where they were vaccinated, such as a doctor’s office or pharmacy, for about 15-30 minutes after a vaccine. That way, they can be monitored for side effects.  

Which arm should you get your vaccine in? Dr. Elbe recommends getting vaccinated in your dominant arm because you use it more. “We want you to move that arm and use that muscle to help distribute the vaccine better and hopefully help prevent soreness,” she says.  

How long does your arm hurt after a vaccine?

“Arm pain is likely to begin within 24 hours of vaccination and lasts a few days after the vaccine is administered,” says Anderson. 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.

Here’s how long injection site soreness can last for common vaccines:

COVID-19 vaccine or booster: 1-3 days
Influenza vaccine: 1-2 days
Varicella vaccine: 1-3 days
Pertussis vaccine: 1-3 days
MMR Vacine: 1-3 days
Pneumococcal vaccine: 1-3 days

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

What is COVID arm?

You may have heard of COVID arm and are concerned it will happen to you. COVID arm is a local reaction by your immune system, meaning it occurs around the injection site. Injection site swelling and redness from a COVID vaccine should dissipate within one to three days, while COVID arm symptoms usually last four to five days. However, according to a report in JAMA, symptoms of COVID arm can last up to 21 days with the Moderna vaccination. 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,” explains Vino Palli, MD, founder of MiDoctor Urgent Care in New York City. 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—aka arm pain.

“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.

8 ways to treat arm pain after a vaccine

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: 

1. Use a cold compress on the injection site Applying a cool compress or wet washcloth on the arm where you got the shot may help relieve pain and discomfort at the injection site.
2. Move your arm around frequently throughout the day to reduce pain.
3. Take over-the-counter (OTC) pain medications, such as Advil (ibuprofen) and Tylenol (acetaminophen) if approved by your provider before and after the vaccination at appropriate intervals.
4. Use antihistamines such as Benadryl if you experience itchiness.
5. 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. 
6. Relax your arm before your shot. Injections into clenched muscles can cause more pain.
7. Request ice or a numbing spray before your vaccination.
8. Engage in gentle exercise. Gently stretch or take a walk to get the blood flowing can help minimize pain. Or you can try specific arm exercises, including: 

• Lateral deltoid raise: Starting with your palms touching the sides of your body, raise your arms straight all the way up to your shoulders. 
• Overhead press: With your arms bent at the elbows and your hands near your shoulders, straighten your arms while lifting them over your head.

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. 

When to see a doctor

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 serious vaccine side effects 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, causing pain, redness, and injection site nodules. 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. 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. 

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.