Comparative histopathological features of cutaneous adverse reactions after COVID-19 mRNA- and viral vector-based vaccines

Abstract

Background: Specific clinical patterns of cutaneous adverse reactions after COVID-19 vaccines have been well-documented as more people become vaccinated. The author group could experience coherent histopathological features categorized into vascular dominant and epidermal dominant patterns in the cases of cutaneous reactions after COVID-19 vaccinations. The purposes of the study were to evaluate the histopathologic patterns of cutaneous reactions after COVID-19 vaccination and speculate on the possible difference in histopathological features between viral vector- and mRNA-based vaccines. From February 2020 to December 2021, a total of 10 cases of cutaneous adverse reactions after COVID-19 vaccination was enrolled and investigated for the study. Regardless of cutaneous morphologies, our cases could be classified into two major subgroups based on location of dominant histopathologic findings. Vascular dominant pattern was shown in four cases, with perivascular reactions with relatively dormant epidermis, while others showed epidermal dominant pattern, with remarkable epidermal changes. Onset of reaction after vaccination was 20.00±11.80 days and 8.17±8.86 days, respectively. The group of the vascular dominant pattern was comprised of three viral vector-based (75.0%) and one mRNA-based (25.0%) vaccine. The epidermal dominant pattern was composed of one viral vector-based (16.7%) and five mRNA-based (83.3%). In conclusion, the types of COVID-19 vaccines, viral vector- and mRNA-based ones, might be one of the determining factors for histopathological features of cutaneous adverse reactions after COVID-19 vaccines. The underlying mechanisms of different histopathological findings between viral vector- or mRNA-based vaccines will be further investigated in our subsequent study.