Soreness and swelling at the injection site are common reactions to the Moderna and Pfizer-BioNTech COVID-19 vaccines. Sometimes, these common symptoms are followed by a less-common itchy rash and other symptoms. This later reaction is known as COVID arm.

COVID arm can be uncomfortable, but it’s rare, and harmless. It typically occurs around 1 week after vaccination from the first or second shot.

COVID arm is mostly associated with the Moderna vaccine.

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

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 may also cause COVID arm but appears less likely to do so. The Johnson & Johnson vaccine has not been associated at all with this side effect.

COVID arm is a delayed hypersensitivity skin reaction that occurs on or around the injection site. Its symptoms show up several days to 1 week or more after the first or second vaccination.

One 2021 case study of people with this condition found that COVID arm symptoms appeared 7 days after the first shot, and 2 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 around the world are getting vaccinated, so even small occurrences of vaccine reactions and side effects are getting lots of attention.

COVID arm is thought to be an immune system reaction. Your immune cells are responding to the muscle cells which 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.

The symptoms of COVID arm typically last from 3 to 5 days. COVID arm won’t escalate to a life threatening condition or serious allergic reaction. It is not associated with anaphylaxis.

Usually, the symptoms of COVID arm resolve on their own. However, if your symptoms are severe or if you feel very uncomfortable or worried, talk with a medical professional. They may be able to recommend medications, such as prednisone, that can help your symptoms resolve quickly.

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. In some instances, your doctor or vaccination provider may recommend you alternate 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:

COVID arm is a minor annoyance which 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.

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.

COVID arm is a delayed hypersensitivity reaction that occurs mostly from the Moderna vaccine. Onset is typically around 1 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.