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Vaccine Patients Experiencing ‘Vaccine Arm’ Days After Injection

Dermatology TimesDermatology Times, April 2021 (Vol. 42, No. 4)
Volume 42
Issue 4

Increasing reports have surfaced of vaccine recipients experiencing delayed cutaneous side effects after receiving the first dose. Experts assure that while the delayed side effect is uncomfortable, it is temporary and can be treated at home.

While the coronavirus 2019 (COVID-19) vaccine is currently being rolled out, some vaccine recipients are experiencing adverse effects (AEs), one of which includes a delayed large local reaction.

This particular reaction is characterized by pain and swelling in the upper arm located at the injection site appearing 7 to 8 days following injection. While this side effect is being commonly referred to as “COVID arm,” experts are warning against this term since the reaction is not caused by COVID-19, but rather by the vaccine.

Esther Freeman, MD, director of global health dermatology at Massachusetts General Hospital, Boston, Massachusetts, spoke with Dermatology Times® about her recently published case series in the New England Journal of Medicine (NEJM)1 regarding these delayed reactions. She suggested calling this delayed reaction “vaccine arm.” She also added that while a majority of reports of this side effect has been seen in Moderna (mRNA-1273) patients, this reaction has also been seen in a few individuals who have received the Pfizer mRNA vaccine.

“People were expecting to see local site injection reactions after the vaccines. What's been surprising is that with Moderna, people are seeing skin reactions on the vaccinated arm appear not within hours or a day of injection, but instead 8 days later. What surprised everyone was this delay in onset.”

Freeman said these reactions are not worrisome and typically go away on their own. Other recommended treatment for the reaction includes topical steroids and oral antihistamines.

In the case series, researchers observed 12 patients who received one dose of the mRNA-1273 vaccine and presented “vaccine arm” with a median onset at day 8 (range, 4 to 11 days).

The report stated that most patients received treatment for their symptoms which comprised of ice and antihistamines. Meanwhile, other patients were treated with glucocorticoids (topical, oral, or both), and 1 patient received antibiotics for suspected cellulitis. Overall, patients’ symptoms resolved in a median of 6 days following onset (range, 2 to 11 days).1

Researchers also performed a biopsy on a patient with “vaccine arm” who was not a part of the 12 other patients for suspicion of delayed-type or T-cell–mediated hypersensitivity, and results were consistent with delayed cutaneous hypersensitivity, according to Freeman.

“I think it's important for people to know this isn't the only reaction that we're seeing in Moderna, but I think this was one of the more surprising reactions, and I think it was also potentially underreported in the Moderna trial,” Freeman said.

She added, “I think the other reason it's important for people to recognize this reaction is that some patients were unnecessarily treated with antibiotics, because people thought this was cellulitis. Being able to provide reassurance to people that this is not an infection, and that it really does resolve on its own without antibiotics, is key.”


Researchers for the case series encouraged all 12 patients to receive a second dose of the mRNA-1273 because neither local injection-site reactions nor delayed-type hypersensitivity reactions were contradictions to subsequent vaccination.

The report states half of the observed patients did not have a recurrence of “vaccine arm”, while 3 patients had recurrent reactions that were consistent with their reactions after the first dose, and 3 other patients had recurrent reactions that were less severe than those following the first dose. Also, researchers observed an earlier onset of recurrent reactions after the second dose with a median onset of 2 days (range, 1 to 3 days).1

“It really addresses the concern both by patients and providers after they saw this reaction after dose one,” Freeman said. “I think people were very worried that it was going to lead to the anaphylaxis or something more severe. With dose two, it was in fact quite the opposite, only half of people got it the second time around, and if you did get it, it was less severe. So, we do encourage patients to go ahead and get their second dose.”


When it comes to managing patient expectations in a time where misinformation and conspiracies run rampant regarding COVID-19 and the vaccine, it can be difficult to communicate with patients the importance of getting vaccinated while also fielding their concerns.

Freeman suggests health care professionals (HCPs) try to understand why the patient is having a particular concern about the vaccine in order to address where they're coming from.

“There's a lot of good resources around the concept of vaccine hesitancy, both from the CDC and elsewhere. We need to really try to understand where patients are coming from. People have legitimate concerns about vaccines, and it’s important to acknowledge that their background or their history or their friends or family members experiences that may be informing their concern,” Freeman said. “So, I think the first step is really to understand what each individual’s concerns are, and why they have that concern, so that you can specifically address it. You may not be able to change their perspective on just one visit, but that it can be a journey towards encouraging vaccination.”

However, when the patient’s primary concern is side effects, such as “vaccine arm,” Freeman recommends HCPs communicate balancing the risk of these temporary and uncomfortable side effects versus the risk of getting COVID which could lead to a severe outcome.


Moderna recently announced it had dosed its first participants in a phase 2/3 study (KidCOVE) investigating the mRNA-1273 vaccine in pediatric patients as young as 6 months old.2

“We are encouraged by the primary analysis of the Phase 3 COVE study of mRNA-1273 in adults ages 18 and above and this pediatric study will help us assess the potential safety and immunogenicity of our COVID-19 vaccine candidate in this important younger age population,” said Stéphane Bancel, CEO of Moderna in a press release.2

With the news of “vaccine arm” circulating, this might discourage some people from getting their children vaccinated despite the mildness of the side effect.

“I think time will tell with these trials to see what kind of reactions and how are they different in children. But I wouldn't anticipate that skin side effects per se would be particularly prohibitive in children,” Freeman said.

Those experiencing any side effects from the vaccine are encouraged to report them to the CDC's Vaccine Adverse Event Reporting System (VAERS) system. For healthcare providers with patients who are experiencing cutaneous side effects in particular, healthcare providers are encouraged to enter the vaccine reaction cases into the AAD/ILDS COVID-19 Dermatology Registry.


1. Blumenthal KG, Freeman EE, Saff RR, et al. Delayed large local reactions to mrna-1273 vaccine against sars-cov-2. New England Journal of Medicine. 2021;0(0):null. doi:10.1056/NEJMc2102131

2. Moderna announces first participants dosed in phase 2/3 study of covid-19 vaccine candidate in pediatric population | moderna, inc. Accessed March 18, 2021. https://investors.modernatx.com/news-releases/news-release-details/moderna-announces-first-participants-dosed-phase-23-study-0/

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