What is the ‘COVID arm’, the strange reaction some experience after being vaccinated with Moderna

A few days after being vaccinated, some people have an itchy rash on the arm, swelling of the skin, and even red pimples or hives.

As vaccination campaigns continue to advance in countries where they already have doses, and at a time when vaccines are the international community’s great hope to stop the COVID-19 pandemic, providing them still raises doubts.

From the urgency with which they should have developed under the curious and anxious gaze of the planet, some side effects emerge, some of which, although expected, are surprising by their rarity.

The latest side effect seen in people who have received the Moderna vaccine is the so-called “COVID arm”. A few days after being vaccinated, an itchy rash, swelling of the skin, and even red bumps or hives appeared on your arm. Despite this, the doctors wanted to reassure the population and assured that the spot that appears on the arms is a harmless response of the immune system to the injection which disappears in about a week.

“We want to reassure people that this is a known phenomenon,” said Dr. Esther Freeman, director of global health dermatology at Massachusetts General Hospital. Having a big red spot on your arm for a few days might not be fun, but the reality is that there is no need to panic and there is no reason not to receive the second dose of the vaccine.“.

Oppositions and warnings

A series of documents began to emerge in scientific publications noting this phenomenon.

Indeed, a working group from Massachusetts General Hospital in Boston has just published a document on a phase III clinical trial of the mRNA-1273 vaccine where they provide information on the immediate reactions at the injection site, which have been observed in 84.2% of participants after the first dose. The trial also showed that delayed injection site reactions (defined in this trial as starting on or after the eighth day) occurred in 0.8% after the first dose and in 0.2% after the first dose. first dose. These reactions included erythema, induration and tenderness. The reactions usually disappeared within 4 to 5 days.

“We also observed significant and delayed local reactions to the mRNA-1273 vaccine, with a median onset on day 8 (range 4 to 11) after the first dose. These reactions had a variable aspect, ”they indicated. They reported a series of 12 patients with these reactions, all of which appeared near the injection site after complete resolution of the initial local and systemic symptoms associated with vaccination.

“Our suspicion of delayed type or T cell mediated hypersensitivity was supported by skin biopsy samples taken from a patient with a significant delayed local reaction who was not among the 12 patients described here.said Kimberly G. Blumenthal, lead author of the report.

Since neither local injection site reactions nor delayed type hypersensitivity reactions are contraindications for subsequent vaccination, all 12 patients were challenged to receive the second dose and completed their cycle. vaccination with mRNA-1273. Although half of the patients did not have a recurrence of significant local reactions, three patients had recurrent reactions similar to the initial dose and three patients had recurrent lower grade reactions than after the initial dose.

“Clinicians may not be ready to treat late local reactions to mRNA-1273 vaccine”, Termina Blumenthal. With the expansion of mass vaccination campaigns around the world, these reactions are likely to raise concerns among patients and requests for evaluation. These reactions have not been systematically recognized, recommendations for the second dose of vaccine have varied, and many patients have received antibiotics unnecessarily.

“We hope this letter will encourage further notification and communication regarding the epidemiologic features, causes and implications of these late skin reactions, as this information could allay patient concerns, encourage completion of vaccination, and minimize the risk of injury. use of unnecessary antibiotics, ”he said. .

This swelling of the arm has an official term used by dermatologists and allergists: “delayed skin hypersensitivity”. This is what they call an adverse reaction produced by the immune system which affects the skin which occurs a few days after receiving the application.

Experts point out that the now called “COVID arm” has also appeared on other occasions in people who have received vaccines against tetanus, the vaccine against chickenpox or the MMR vaccine (measles, mumps and rubella). However, this reaction has only been seen when a person has been vaccinated with Moderna’s vaccine, but not when the dose of Pfizer has been given. Despite this, Freeman, one of the leading researchers on skin reactions to COVID-19 vaccines around the world, added that this side effect should not mean any fear among the population, let alone choosing not to receive the. second dose of Moderna’s vaccine, or wanting to receive Pfizer’s dose before Moderna’s.

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