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If you have received a COVID-19 vaccine and developed a swollen red rash at the injection site several days later, you may have developed a “COVID arm”. This nasty (but ultimately harmless) side effect of the coronavirus vaccine is something researchers are now beginning to understand a little better.
The symptoms of what is colloquially known as the COVID arm include redness, swelling and tenderness at the injection site that develop eight or more days after vaccine administration, according to a new report in the New England Journal of MedicineLooking at the data from Phase 3 clinical trials for the Moderna mRNA vaccine, the researchers found that the response usually went away after four or five days.
To put this in perspective, the researchers note that about 84% of the people in the studies experienced a reaction, such as pain, shortly after the injection at the injection site. But only 0.8% of people (244 out of approximately 30,000) experienced these delayed skin reactions after their first dose. But the researchers note that the study data does not provide a complete picture of what those reactions might include and does not differentiate between reactions after the first and second doses of the vaccine.
So the researchers examined 12 case reports of people who developed delayed skin reactions after receiving the Moderna vaccine. Most people noted that their symptoms started on day eight or nine after they received the first dose of the vaccine, but one person’s response appeared on day four and one developed it on day 11. Usually these patients reported itching, redness , swelling and pain. But interestingly, not everyone who developed this response after the first dose got one after the second: of the 12 patients in this study, only half reported having a similar response after the second dose (three of them had more mild responses to the second dose). time around).
While researchers still don’t know exactly what causes this reaction, this pattern of symptoms and a skin biopsy from another patient (who wasn’t one of the other 12 in the study) does provide some clues. The biopsy suggests that the body’s T cells, a type of immune cell that can limit the effects of an invading virus, may be behind these delayed hypersensitivity reactions.
Perhaps the biggest takeaway from these results is that having one of these delayed responses to the first dose of a COVID-19 vaccine doesn’t mean you can’t have the second. “We can now reassure you that it is safe to get the second #moderna vaccine even if you had a delayed major local #skin response to the first shot,” said Esther E. Freeman, MD, Ph.D., director of global health dermatology at Massachusetts General Hospital, an associate professor of dermatology at Harvard Medical School, and one of the study’s authors, wrote on Twitter