Some people are experiencing delayed reactions to the first dose of the Covid vaccine, with their arms turning red, sore, itchy and swollen about a week after the injection.
The reactions, while unpleasant, seem harmless. But the condition of angry-looking skin could be mistaken for an infection, according to a letter published on Wednesday in The New England Journal of Medicine. The doctors said they wanted to share information about the cases to help prevent unnecessary use of antibiotics and to alleviate patients’ concerns and reassure them that they can safely get the second vaccine.
“We modified our patient brochure as soon as we started to see this,” said Dr. Kimberly G. Blumenthal, author of the letter and an allergist at Massachusetts General Hospital, in an interview. “We said it was normal to get red, itchy and swollen when you get the vaccine. We changed the text to say that it can also start seven to 10 days after you receive the vaccine. “
The letter describes the experiences of 12 people who had “delayed local reactions” that started four to 11 days after the first injection of the Moderna vaccine, an average of eight days. The report is not a controlled study, but a series of cases that caught the attention of doctors because the recipients of the vaccine were concerned and wanted to know if they should get the second injection.
Most were vaccinated at Massachusetts General Hospital, where the Moderna and Pfizer-BioNTech vaccines were administered. But the delayed reactions occurred only in people who received the injection of Moderna, said Blumenthal, adding: “I don’t understand why.”
Moderna reported late skin reactions in her large clinical trial in 0.8 percent of recipients after the first dose and 0.2 percent after the second dose.
According to the letter from Dr. Blumenthal and 10 other doctors, all 12 people reported typical symptoms, such as pain in the arm, which usually occurs shortly after inoculation, and the initial symptoms disappeared.
Then, a delayed reaction occurred. In five people, large and elevated skin lesions measuring 10 or more centimeters in diameter near the injection site appeared. Two had skin rashes at other points, one near the elbow and the other on the palm. Some also had systemic symptoms at the same time, such as fatigue and sore muscles.
Most treated skin symptoms with ice and antihistamines. But some needed steroids, in the form of a cream or pill, and others were prescribed an antibiotic by a doctor who mistook the problem for an infection.
What you need to know about the vaccine launch
Symptoms lasted an average of six days, ranging from two to 11 days. All patients started to receive the second injection. Half had no further delayed reaction, but three developed the same symptoms again and three had milder reactions than after the first injection.
Dr. Blumenthal said there were many unanswered questions about the reactions. Ten of the 12 patients were women, but it is not clear whether women are more prone to the problem or whether the imbalance occurred because more vaccinated health workers were women.
Some were allergic to drugs, wasp stings or food, but others were not.
A skin biopsy on a patient indicated that the condition was a reaction to medications. But what exactly the patient’s immune system was reacting to is unknown.
“I hope companies will find that out,” said Blumenthal.
She is aware of about 30 cases now, mostly among women and all recipients of the Modern vaccine so far, she said, and the hospital has created a registry to track them.