Blumenthal et al.1 reported cases of delayed large local reaction to the mRNA-1273 Moderna COVID-19 vaccine, which was called the 'Moderna arm' for the first time. Intriguingly, this phenomenon was… Click to show full abstract
Blumenthal et al.1 reported cases of delayed large local reaction to the mRNA-1273 Moderna COVID-19 vaccine, which was called the 'Moderna arm' for the first time. Intriguingly, this phenomenon was observed primarily in Moderna vaccine, but rarely reported in BNT162b2 COVID-19 vaccine by Pfizer-BioNTech.2-4 Because the reports were limited to mRNA vaccines, a delayed type hypersensitivity reaction to the excipient polyethylene glycol (PEG) in both mRNA vaccines was suggested as one potential etiology.4,5.
               
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