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The One COVID Vaccine Side Effect You Haven't Heard About

It may look scary, but it's harmless.

Most side effects of the COVID vaccine are minor and similar to those reported with other injections, like soreness at the injection site, fatigue and fever. But one unique reaction has raised some eyebrows, although a new study says it's harmless. "COVID arm" — also known as "Moderna arm" — is a delayed-onset rash that appears at the injection site up to a week or so after the shot is given. It can grow to be quite large. About 95% of cases are associated with the Moderna vaccine. Read on for more about this, so you can watch out for it yourself—and to ensure your health and the health of others, don't miss these Signs Your Illness is Actually Coronavirus in Disguise.

Skin Rashes After a Vaccine are Not Thought to be Dangerous

New research published this week in the Journal of the American Academy of Dermatology found that delayed skin responses to the vaccine, which can occur from one to eight days after injection, are not dangerous. They most often happen after the first dose of the vaccine but don't prevent people from completing their vaccination. 

"People can get full-body rashes, and that can be surprising and a little scary, but these patients did extremely well, recovered and were able to go back and get their second dose," said study author Dr. Esther Freeman, director of global health dermatology at Massachusetts General Hospital, in USA Today.

RELATED: Doctors Say "DO NOT" Do This After Your COVID Vaccine

"People Can Feel Reassured About Getting the Second Dose"

"COVID arm" is different than a severe allergic reaction to the vaccine, such as anaphylaxis, a potentially life-threatening swelling of the airway. That usually happens within minutes of the injection, which is why the CDC has advised everyone to wait 15 to 30 minutes after getting the vaccine before leaving the injection site.

But rashes that start later don't signify a serious problem. "For people whose rashes started four or more hours after getting the vaccine, zero percent of them went on to get anaphylaxis or any other serious reaction," said Freeman. "Zero is a nice number."

According to the study, most people who experienced "COVID arm" did not get it again after their second shot. In those who did, it was generally less severe and resolved within three to six days.

"People can feel reassured about getting the second dose of their vaccine," said Freeman, principal investigator for the international COVID-19 Dermatology Registry. "Even if you have a pretty impressive rash after the vaccine, as long as it didn't start within four hours of vaccination you should feel comfortable getting the second dose."

RELATED: Most COVID Patients Did This Before Getting Sick

How to Survive This Pandemic

As for yourself, do everything you can to prevent getting—and spreading—COVID-19 in the first place: Wear a face mask, get tested if you think you have coronavirus, avoid crowds (and bars, and house parties), practice social distancing, only run essential errands, wash your hands regularly, disinfect frequently touched surfaces, and to get through this pandemic at your healthiest, don't miss these 35 Places You're Most Likely to Catch COVID.

Michael Martin
Michael Martin is a New York City-based writer and editor whose health and lifestyle content has also been published on Beachbody and Openfit. A contributing writer for Eat This, Not That!, he has also been published in New York, Architectural Digest, Interview, and many others. Read more about Michael
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