Adverse Reactions to mRNA COVID-19 Vaccines and Studies of the Mechanisms Involved

Abstract

Objective: Characterize the immunologic mechanisms underlying allergic reactions to mRNA COVID-19 vaccines. Material and Methods: A total of 85 adverse reactions induced by mRNA COVID-19 vaccines were recorded and graded in severe, moderate and mild/atypical cases. Skin prick tests and intradermal tests were conducted to authorized vaccines, polyethylene glycol (PEG), polysorbate 80 (P80), and trometamol. Total and specific IgE to ethylene oxide (EO) were obtained. Basophil activation test (BAT) to vaccines and PEG were also conducted. Results: Positive results were obtained mainly among moderate/severe patients, and also in 2 atypical cases. Both P80 and Trometamol were negative in all the cases studied. PEG was positive in 3 cases. Among 83out of 85 cases tested cases with vaccines, 11 were positive by intradermal tests and, no case was positive by prick tests. Among the 15 selected patients with positive skin tests and/or severe symptoms, 9 of them presented positive results in BAT. Conclusions and Relevance: Among mild and atypical cases, those with negative skin tests tolerated vaccines with premedication. Women and people with a history of adverse drug reactions appear to be at increased risk of ADRs and allergy to the mRNA vaccine. The most serious cases, however, have been recorded in the only two men in the series. Allergy to PEG has only been confirmed in 3% of the adverse reactions and less than 1 per 100,000 vaccines administered. Immunological tests results suggest different induction mechanisms are involved.