Elected Vice President Kamala Harris on Tuesday received her first dose of the Moderna COVID-1

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There is good news about “Modern arm”, the swollen, sometimes itchy red rash that some people get a week or so after being vaccinated with Modern’s COVID-19 vaccine.

There were concerns that people who experienced the irritating rash might have a worse reaction with the second dose. A report published on Wednesday finds that this is not the case – and most have no reaction at all the second time.

“We encourage people who have had this reaction to go in and get their second shot,” said Dr. Kim Blumenthal, an allergist, epidemiologist and professor of medicine at Harvard Medical School who tracks the reaction.

“There was concern that if you had the reaction to the first dose, it could happen again with the second and possibly be worse. But we have now followed enough cases to know that it does not happen.”

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The reaction appears as an angry red rash, almost always on the arm where the vaccine was given, but can spread to other parts of the arm or hand. It can be a very pronounced oval on the skin, hard and hot to the touch and sometimes it is very itchy.

The reaction only occurs in people receiving the Moderna vaccine, not in Pfizer-BioNTech. It is more common in women than men and is seen more often in people under 60 years of age.

For Natalie Roth of San Mateo, California, the area where she got her first COVID-19 vaccine shot was “swollen and hot to the touch, but not so much,” she said. The red pletch grew every day but never itched and lasted for about six days.

The reaction may come as a surprise because it typically does not appear until seven or eight days after immunization.

“In all patients, they had completely resolved any initial symptoms when they first got the shot, and then this emerged from nowhere,” Blumenthal said.

Rash is now called “delayed large local reaction”, although many patients have begun to informally refer to it as “Modera arm”.

Doctors and patients only began to hear reports of the reaction shortly after the Moderna vaccine began to be distributed. USA TODAY wrote about it on January 27, but at that time there was little data available.

Blumenthal and Dr. Esther Freeman has tracked the phenomenon and published the first article about it in the New England Journal of Medicine on Wednesday.

They have been following cases of the reaction at Massachusetts General Hospital and have not seen cases where the reaction worsened with the second shot.

“This paper needs to be really reassuring for both patients and healthcare providers,” Freeman said. “The reaction only seems to occur in about half of the cases, and under no circumstances did we see it get worse.”

I ca. In 50% of cases, the patient had no reaction at all with the second dose. In 25%, the reaction was milder; in 25% it was about the same.

“The big concern that people might have had was that they were going to have a full-body, full-blown allergic reaction. But at that point, we can be reassuring,” said Freeman, director of global health dermatology at Massachusetts General and professor at Harvard Medical School.

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Another positive finding was that in people who got rashes with both shots, it seemed to fade faster after the other.

Those who had it after the first shot reported the rash lasted for six to 11 days. Those who had the reaction after the second shot said it faded within two to three days, Freeman said.

Wendie Holman’s first rash lasted for 10 days, but the second lasted only three.

“Today, if I look closely, I see a faint remnant of pink skin around the graft site. There is no itching and no pain,” said Holman, a resident of Santa Rosa, California.

So far, the side effects of both the Moderna and Pfizer BioNTech vaccines appear to be almost identical except for this one reaction. Experts warn that a small number of people having a reaction is not a reason to prefer one vaccine over another. People should take the vaccine they can get, Freeman said.

The treatment is simple for most patients. Ice at the site of rash and non-sedative antihistamines are usually all that is needed to deal with the symptoms, Blumenthal said. Getting the second shot on the opposite arm can help, but it is not necessary.

In a few, more severe cases, steroids were needed. The good news is that in a few cases, patients had not repeated rashes with their second-dose vaccine, she said.

Doctors reported that some patients were being treated with antibiotics when the rash was misdiagnosed as an infection.

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It is not known how common the reaction is. In the initial Moderna tests, “delayed injection site reactions” occurred in 0.08% of participants. However, Freeman believes the number is likely to be higher because Moderna only counted responses that began on or after day 8.

Such delayed skin reactions to vaccinations are rare, but have been reported with other routine vaccinations, she added.

Researchers are urging those experiencing the reaction to report the Centers for Disease Control and Prevention’s vaccine side effect system, known as V-safe.

Doctors continue to study the reaction and are particularly interested in collected images of rashes in people with darker skin tones. There are no indications that the reaction is different in people with darker skin; they will simply document the phenomenon across all skin tones.

Contact Elizabeth Weise at

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