For many who get an mRNA COVID vaccine like Moderna or Pfizer-BioNTech, arm soreness is a common experience post-vaccination. But in some cases, there's also what's being called "COVID arm."
"COVID arm" is used to describe delayed skin reactions such as rashes, which appear days after injection.
"If it is going to arise, it usually appears about a week after your vaccine,” Dr. Brita Roy, an internal medicine physician and director of population health for Yale Medicine said. “It‘s a red, swollen area at the site of the shot."
The skin reactions gained attention when a letter was published in the New England Journal of Medicine earlier this month detailing some patients who experienced varying degrees of arm rashes following their first dose of the Moderna vaccine.
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According to data from a Phase 3 trial of the Moderna vaccine, reported in the journal's letter, delayed injection-site reactions - defined in the trial as those with an onset on or after day eight - were reported in 244 of the 30,420 participants following the first dose and in 68 participants after the second dose. The reactions typically resolved after four to five days and those who experienced them following the first shot were recommended to still receive their second dose.
“It’s not super common, but it’s not uncommon. It’s a delayed hypersensitivity, similar to what you may see if you get poison ivy,” Roy said. “You maybe came into contact with the poison ivy in your yard, but some people won’t get a rash until a few days later.”
The Centers for Disease Control and Prevention has acknowledged reports "that some people have experienced a red, itchy, swollen, or painful rash where they got the shot," which it identified as "COVID arm."
According to the CDC, the rashes can start within a few days to more than a week after the first shot and "are sometimes quite large."
"If you experience 'COVID arm' after getting the first shot, you should still get the second shot at the recommended interval if the vaccine you got needs a second shot," the CDC noted. "Tell your vaccination provider that you experienced a rash or 'COVID arm' after the first shot. Your vaccination provider may recommend that you get the second shot in the opposite arm."
Chicago Department of Public Health Commissioner Dr. Allison Arwady said such side effects have not yet raised concern.
"What has been interesting, I think, is that this has really raised some awareness for wanting to make sure that we're asking questions," she said during a Facebook Live Thursday.
"I'm glad that people are looking at it, but I don't want people to feel like there's something dangerous about it that we've not detected," Arwady added.
According to a report in the American Academy of Dermatology Association, the skin reactions have been seen "predominantly from the Moderna vaccine."
"We have seen a presentation about five to nine days after the first vaccination with what has been referred to in the media as COVID arm," Christen Mowad, chair of dermatology at the Geisinger Medical Center in Pennsylvania wrote. "It presents with significant redness, induration, and sometimes warmth, typically in a circular pattern at the injection site with some patients presenting to their doctors thinking it is cellulitis. It is often itchy."
Mowad also noted that the reaction has been seen commonly in women.
So what can you do if you get it?
The CDC said those who experience COVID arm can take an antihistamine.
"If it is painful, you can take a pain medication like acetaminophen or a non-steroidal anti-inflammatory drug (NSAID)," the CDC recommends.