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Study of Covid-19 vaccine skin reactions shows no serious adverse events

Research led by the Harvard Medical School found that while patients developed a wide variety of cutaneous reactions following Covid-19 mRNA vaccinations, patients did not experience serious adverse events after the first or second dose of the vaccine. Further, most patients with first dose reactions did not develop a second dose reaction.

Results of the study were published online ahead of print in the Journal of the American Academy of Dermatology (April 7, 2021).

"We understand that some of these reactions may look scary, but when they appear more than four hours after receiving a Covid-19 vaccine, they are typically minor and in some cases, may indicate the body’s immune system is doing a good job of responding to the vaccine," said Dr. Esther Freeman, a senior author of the study, in a press release. "Some rashes may appear a day or two after vaccination, and some have a delayed onset, as long as seven to 14 days after vaccination. Most of these rashes resolve on their own with time or—depending on the rash—may require oral antihistamines, topical steroids, or other treatments as directed by a physician."

Dr. Freeman, the director of Global Health Dermatology at Massachusetts General Hospital and principal investigator of the international Covid-19 Dermatology Registry, added that any reactions that start immediately after vaccination, or within four hours of the shot, need to be taken seriously, and patients experiencing these rare type of allergic symptoms should seek prompt medical attention, as recommended by the CDC.

To evaluate the morphology and timing of cutaneous reactions after mRNA Covid-19 vaccines, the study’s authors conducted a study collecting cases of cutaneous manifestations after Covid-19 vaccination.

From Dec. 2020 to Feb. 2021, researchers recorded 414 cutaneous reactions to mRNA Covid-19 vaccines from Moderna (83%) and Pfizer (17%).

Delayed large local reactions were the most common type of reaction reported, followed by local injection site reactions, urticarial eruptions, and morbilliform eruptions. Forty-three per cent of patients with first dose reactions experienced second dose recurrence.

Dr. Freeman notes that some patients developed pernio/chilblains, referred to as ‘Covid toes’, following their Covid-19 vaccine. She adds this is of interest since it shows that the vaccine is triggering a similar immune response that has been seen in patients after the virus. While the reactions can be uncomfortable for the patient, Dr. Freeman said it shows that the patient’s body is mounting an immune response to the vaccine, which, in some cases, can show up on the patient’s skin.

“Through this research, we have a deeper understanding of how the Covid-19 vaccine affects the patient and their skin,” said Dr. Freeman. “I hope our findings, which show that patients tolerated vaccination well even when they did develop skin side effects, offer greater reassurance for anyone hesitant to get vaccinated.”

In addition to studying skin reactions resulting from Covid-19 vaccines, the researchers assessed patients’ responses from the first dose to the second. Results showed that less than half of the people who experienced skin reactions after the first dose experienced a reaction after the second, and if they did, it was milder.

“I hope this information encourages more people to get their second dose of the Covid-19 vaccine even if they experienced a skin reaction after their first dose,” said Dr. Freeman. “The Covid-19 vaccine will help protect patients from getting the virus and can also prevent them from getting very sick if they do get infected.”

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