Delayed Large Local Reactions to mRNA-1273 Vaccine against SARS-CoV-2

Abstract

Baden et al.¹ report on a phase 3 clinical trial of the mRNA-1273 vaccine against SARS-CoV-2, and they provide information on immediate injection-site reactions, which were observed in 84.2% of the participants after the first dose. The trial also showed that delayed injection-site reactions (defined in that trial as those with an onset on or after day 8) occurred in 244 of the 30,420 participants (0.8%) after the first dose and in 68 participants (0.2%) after the second dose. These reactions included erythema, induration, and tenderness. The reactions typically resolved over the following 4 to 5 days. However, these reactions were not further characterized, and links between reactions after the first dose and those after the second dose were not provided to inform clinical care.