Delayed local reaction with subcutaneous infiltration after vaccination with mRNA-1273—a previously undescribed reaction pattern of COVID arm

Abstract

The mRNA-1273 vaccine against SARS-CoV‑2 was approved in Europe in early 2021. Meanwhile, there are a number of case reports of delayed local reactions after vaccination (“COVID arm”). In these reports, superficial lymphocytic infiltrates were described, but no involvement of the deep dermis or subcutis. We report the case of a healthy 32-year-old man with involvement of the deep dermis and subcutis after vaccination with mRNA-1273. This case is the first to show a delayed T‑cell mediated reaction with a deep pattern of reaction, with the dermal perivascular and periadnexal infiltrate extending from the papillary dermis into the deep reticular dermis and subcutis. The infiltrate was predominantly lymphocytic with an admixture of histiocytes and neutrophil granulocytes, scattered mast cells and sparse eosinophil granulocytes.