Covid Arm: Causes, Safety, Treatment, And More - Healthline

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COVID-19

Covid Arm After Moderna or Pfizer Shot: What to Know

Medically reviewed by Angelica Balingit, MD — Written by Corey Whelan — Updated on May 19, 2023

Symptoms
Cause
After a booster
Duration
Treatment
Vaccine safety
When to call a doctor
Takeaway

COVID arm is a harmless delayed skin reaction to the COVID vaccine. It happens about one week after the first or second shot of the Moderna vaccine but may also occur after Pfizer. If you didn’t get it before, you’re less likely to get it after a booster shot.

This time of year, you may be planning to get the latest booster of the Moderna or Pfizer-BioNTech COVID-19 vaccine along with your annual flu shot.

If you experience soreness, redness, swelling, or an itchy rash at the injection site about a week after getting the booster, you likely have COVID arm.

COVID arm is a rare reaction. It typically occurs around one week after the first or second shot vaccination. While not impossible, it is less likely to occur with a booster shot if you haven’t experienced it before.

It is mostly associated with mRNA vaccines like Moderna and Pfizer. Most of the known reactions have occurred with Moderna. Unlike an immediate allergic reaction, this delayed reaction is not serious and does not mean you should avoid getting a booster shot.

In this article, we’ll clue you in on the symptoms and treatments of COVID arm. We’ll also explain why it happens.

Symptoms

COVID arm is a harmless immune system reaction that some people have after getting the Moderna vaccine. A 2021 case report showed that the Pfizer-BioNTech vaccine might also cause COVID arm but appears less likely to do so. The Johnson & Johnson vaccine or the recently approved Novavax have not been associated with this side effect.

COVID arm is a delayed hypersensitivity skin reaction that occurs on or around the injection site. Its symptoms appear several days to a week after the first or second vaccination.

One 2021 case study of people with this condition found that COVID arm symptoms appeared seven days after the first shot and two days after the second.

Symptoms of COVID arm include:

itching, which can be intense
a red or discolored rash that varies in size from quarter-sized to very large
in some instances, the rash may spread to your hands or fingers
swelling
pain
skin feels warm to the touch
hard lump under your skin where the injection took place

If you’re hearing about COVID arm a lot, you may be concerned that you will have this reaction. Keep in mind that COVID arm is relatively rare and never dangerous.

Millions of people worldwide are getting vaccinated, so even small occurrences of vaccine reactions and side effects are getting lots of attention.

Why does this happen?

COVID arm is thought to be an immune system reaction. Your immune cells respond to the muscle cells that have absorbed the mRNA vaccine.

The vaccine produces the SARS-CoV-2 spike protein, which the immune system thinks is an infection that needs to be fought. This is referred to as an overexuberant immune response.

Since the COVID-19 vaccines are new, we don’t know definitively what exact mechanism triggers COVID arm symptoms. This reaction and others are continuing to be studied worldwide.

Can it happen after a booster shot?

If you haven’t experienced COVID arm before after getting your first shot, you’re even less likely to get it now.

Less than 50% of people who got COVID arm after their first dose will get it after their second. It is probably even less likely to happen after subsequent booster doses.

Even if you have gotten COVID arm before, this should not stop you from getting another booster dose. COVID arm may feel mildly uncomfortable, but the reaction is not dangerous and will clear on its own.

How long does it last?

The symptoms of COVID arm typically last about 5 days but may last as long as 21 days. It won’t escalate to a life threatening condition or serious allergic reaction and is not associated with anaphylaxis.

Usually, the symptoms of COVID arm resolve on their own. However, talk with a medical professional if your symptoms are severe or if you feel very uncomfortable or worried.

Can you treat it?

Treating COVID arm will not reduce your immune system’s response to the vaccine. Your immune system has already indicated it’s responding robustly.

COVID arm should also not stop you from getting your second shot. Sometimes, your doctor or vaccination provider may recommend alternating arms if you had a strong skin reaction to your first vaccine.

Even though it’s not serious, COVID arm can be uncomfortable. At-home treatments that reduce pain, swelling, and itching include:

cool compresses
topical steroids
topical pain medication
oral antihistamines
acetaminophen or nonsteroidal anti-inflammatory drugs (NSAIDs) such as ibuprofen (Advil, Motrin).

Why you should still get a vaccine

COVID arm is a minor annoyance that will disappear within a few days. COVID-19 is a life threatening condition, and the vaccine is highly protective against the virus SARS-CoV-2, which causes COVID-19.

Multiple studies have found that COVID-19 vaccines, including boosters, are safe, and that adverse reactions are rare.

A recent study by the National Institute of Health (NIH) also found that these vaccines are effective, leading to a low hospitalization rate with severe symptoms or death from COVID-19.

If you’re worried about COVID arm, keep in mind that the protective benefits of the COVID-19 vaccine far outweigh the risks associated with COVID arm or developing COVID-19 itself. It’s also important to talk with your doctor to learn more about the COVID-19 vaccine.

When to call a doctor

Anaphylaxis from a COVID vaccine is also very rare, occurring in only 5 cases per one million administered vaccines, which means the vaccine’s benefit still outweighs the risk. However, if you do experience a severe allergic reaction, it will usually happen immediately after receiving the injection.

Another complication of the mRNA vaccine can be myocarditis. While less rare than anaphylaxis, this is still pretty uncommon.

If you do experience anaphylaxis symptoms or symptoms of myocarditis after getting COVID vaccine, you should seek immediate help.

Other skin reactions can also occur after getting the shot that may look like COVID arm but develop closer to the time you get the shot. They may happen right after, within a day, or within 2-3 days. They may also affect other parts of the body.

Any severe skin reaction after the vaccine is also very rare. But any time you experience skin symptoms, it’s a good idea to speak with your doctor.

The bottom line

COVID arm is a delayed hypersensitivity reaction that occurs mostly from the Moderna vaccine. Onset is typically around one week after vaccination. Itching, pain, and swelling are the main symptoms.

COVID arm is a relatively rare occurrence, which should not be confused with the early onset arm reactions caused by many vaccines. It resolves on its own within a few days.

You may want to consider talking with your doctor to learn more about the COVID-19 vaccine’s benefits and side effects.

How we reviewed this article:

SourcesHistoryHealthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical journals and associations. We only use quality, credible sources to ensure content accuracy and integrity. You can learn more about how we ensure our content is accurate and current by reading our editorial policy.

Allergic reactions after COVID-19 vaccination. (2022).https://www.cdc.gov/coronavirus/2019-ncov/vaccines/safety/allergic-reaction.html
Coronavirus (COVID-19) Update: FDA authorizes emergency use of Novavax COVID-19 vaccine, adjuvanted. (2022).https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-emergency-use-novavax-covid-19-vaccine-adjuvanted
Elyoussfi DS, et al. (2021). Skin reactions to COVID-19 vaccines. .https://dermnetnz.org/topics/skin-reactions-to-covid-19-vaccines
Gambichler T, et al. (2022). Cutaneous findings following COVID‐19 vaccination: Review of world literature and own experience.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8656409/
Johnston MS, et al. (2021). Delayed localized hypersensitivity reactions to the Moderna COVID-19 vaccine a case series.https://jamanetwork.com/journals/jamadermatology/fullarticle/2779643
Kelly JD, et al. (2022). Incidence of severe COVID-19 illness following vaccination and booster with BNT162b2, mRNA-1273, and Ad26.COV2.S vaccines.https://pubmed.ncbi.nlm.nih.gov/36156706/
Lindgren AL, et al. (2021). COVID arm: Delayed hypersensitivity reactions to SARS-CoV-2 vaccines misdiagnosed as cellulitis. https://journals.sagepub.com/doi/10.1177/21501327211024431?url_ver=Z39.88-2003&rfr_id=ori:rid:crossref.org&rfr_dat=cr_pub%20%200pubmed
Ramos CL, et al. (2021). “COVID arm”: Very delayed large injection site reactions to mRNA COVID vaccines.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8056968/
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Wei N, et al. (2021). “COVID” arm: A reaction to the Moderna vaccine.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7959672/

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Medically reviewed by Angelica Balingit, MD — Written by Corey Whelan — Updated on May 19, 2023

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