Researchers at Massachusetts General Hospital (MGH) are calling for more awareness of delayed skin reactions that occur in some patients who receive the Moderna mRNA-1273 Covid-19 vaccine.
In a letter to the editor published online ahead of print in the New England Journal of Medicine (March 3, 2021), the authors note Phase 3 clinical data from the Moderna vaccine trial showed delayed skin hypersensitivity in a small number of the more than 30,000 trial participants.
The authors note the large, red, sometimes raised, itchy or painful skin reactions were never fully characterized or explained. They warn that clinicians may not be prepared to recognize these effects and guide patients on treatment options and completion of the second dose of the vaccine.
“Whether [the patient has] experienced a rash at the injection site right away or this delayed skin reaction, neither condition should prevent [them] from getting the second dose of the vaccine,” said Dr. Kimberly Blumenthal in a press release. “Our immediate goal is to make physicians and other care providers aware of this possible delayed reaction, so they are not alarmed, but instead well-informed and equipped to advise their patients accordingly.”
Dr. Blumenthal is the lead author of the letter and co-director of the Clinical Epidemiology Program in the division of Rheumatology, Allergy and Immunology at MGH.
In the letter, Dr. Blumenthal and her co-authors included their clinical observations of the delayed, large, local reactions to the Moderna vaccine, and report on a series of 12 patients with the reactions.
Of the 12 patients, symptom onset ranged from four days after the first dose up to 11 days following vaccination, with a median onset of symptoms on day eight. The size and severity of the reactions varied. Most patients were treated with ice and antihistamines, although some required corticosteroids and one was erroneously treated with antibiotics.
“Delayed cutaneous hypersensitivity could be confused—by clinicians and patients alike—with a skin infection,” said Dr. Erica Shenoy, a co-author of the letter. “These types of reactions, however, are not infectious and thus should not be treated with antibiotics.”
Dr. Shenoy is the associate chief of the MGH Infection Control Unit.
Patient symptoms cleared up after a week for the group of 12 reported in the letter, the authors wrote. Half of the patients went on to experience a reaction after the second dose—at or around 48 hours post-vaccination. No patient experienced a reaction to their second dose that was more severe than their first reaction.
The authors wrote that skin biopsies confirmed their suspicion of a delayed allergic immune response commonly seen in drug reactions.
“For most people who are experiencing this, we believe it is tied to the body’s immune system going to work,” said Dr. Esther Freeman, a co-author of the letter. “Overall, this data is reassuring and should not discourage people from getting the vaccine.”