Is 'COVID Arm' Actually Dangerous?

There's an unexpected side effect occurring in some people who have received a COVID-19 vaccine — a delayed reaction at the injection site that has been dubbed 'COVID arm.' Dermatologist Dr. Elizabeth Houshmand, FAAD, explains (via NBC DFW): "It's happening about seven to 10 days after [the injection]. It's mounting an immune response and what we are seeing are swollen red patches on the same arm that you receive the vaccine on."

The majority of 'COVID arm' reactions have been reported by those who have received the Moderna COVID-19 vaccine, but a small number of similar reactions are also being reported by those receiving the Pfizer-BioNTech, Oxford-AstraZeneca, and Novavax vaccines (via Psychology Today). Pain and itchiness at the injection site, as well as enlarged axillary (armpit) lymph nodes are also being reported.

Medical experts point out that these reactions are generally not a cause for alarm. Dermatologist Edward Jeffes, M.D., Ph.D., says "Those delayed-type hypersensitivity reactions, when localized, are typically not serious and disappear after a few days to a week or so."

'COVID arm' is more common after the Moderna vaccine

Percentage-wise, the numbers of COVID-arm reactions are fairly low. During clinical trials, of the 15,181 people injected with the Moderna vaccine, 244 experienced a delayed injection-site reaction after the first dose, and 68 after the second dose.

But important questions remain unanswered. Why does the Moderna vaccine induce this particular reaction more than the other vaccines? And is it the mRNA itself, or another vaccine ingredient, that is the main culprit? It's possible that we can expect to learn more about reactions to these types of vaccines as the weeks go by.

For those who experience 'COVID arm,' the CDC recommends going ahead with the second dose of the vaccine, but getting it in the other arm. Houshmand suggests treating the swollen site with an ice pack, or taking a pain reliever or antihistamine with your doctor's approval. She adds, "It's uncomfortable, but I wouldn't let it stop you from getting the vaccine."