Some patients have reported developing a rash-like side effect after receiving the Moderna vaccine which has quickly been dubbed 'Covid arm'.
The jab, which is not yet available in the UK, is said to have caused itchiness and irritations in the days afterwards among a small number of people.
One woman said her reaction was so severe she's having second thoughts about getting the second dose - but doctors have quickly moved to allay any fears, The Mirror reports.
Amelia Brown, who lives in Visalia, California sent FOX26 pictures of her arm just days after getting her first dose of the vaccine on January 11.
She said: "They gave me the shot, I actually didn’t even feel it to be honest."
Shortly afterward however, she began to feel dizzy and had a minor allergic reaction.
“In an over abundance of caution, they had me go and visit the hospital just to ensure that I was ok," said Brown, "I was, I’m here, I’m happy and the next day I went to work, not a problem,” she said.
Brown added the injection site was tender for a few days afterward, but it was nothing major.
However, exactly one week after her first dose, she says the area became itchy and irritated. The next morning, a lump appeared on her arm.
She said: “It was just red and angry and had hives. Like you could feel the bumps.
“It had just grown overnight from like, a dollar size to like, a baseball size.
"And it was very swollen, hot to the touch, sore, even if I wore my coat that day, the pressure of the coat was painful."
Brown says she spoke with a few different medical professionals who advised her to leave it alone unless it got worse.
Dr Praveen Buddiga, an immunologist in the region, said: "'Covid arm' is basically a delayed type of hypersensitivity or an allergic reaction that occurs about probably 7 to 10 days afterward."
The doctor assured that he sees this in about 2% to 9% percent of patients.
"They should see their doctors if it doesn’t go away in 48 hours," said Dr. Buddiga.
He also recommends that patients with 'Covid arm' do three things and said "Just use the method of putting ice on it, drink a lot of water, and stretch that arm and it’ll go away in less than 24 hours."
“It’s very important they get the second dose,” said Dr Buddiga warned.
“We have not seen a lot of those, we have seen a couple, it’s a local response and it seems to resolve within 24 hours that it shows up,” said Rick Lembo who's the Director of Sports Medicine at Sierra Pacific Orthopedics, where some vaccines are being administered.
The Moderna vaccine was approved on January 7, but is not expected to be available in the UK until spring and 17 million doses are on order.
The vaccine was nearly 95 per cent effective in trials.
