Type I hypersensitivity to mRNA-vaccines against SARS-CoV-2

ABSTRACT

Background: To describe anaphylactic/anaphylactoid reactions induced by mRNA-vaccines against SARS-CoV-2 and immune-allergic studies carried out. Method: Twenty two patients were referred prior to the administration of the second dose of vaccine. Skin tests were performed to both mRNA vaccines (Pfizer and Moderna1/1), different sources of poliethylenglycol (PEG), Polysorbate 80 and Trometamol. Total IgE, specific IgE to ethylene oxide, tryptase and Basophile activation test (BAT) were performed to the same reactives including both Pfizer and Moderna vaccines adding PEG2000. Results: Four anaphylaxis/anaphylactoid reactions are documented. One of them with the entire study negative. The remaining three cases were non-severe anaphylaxis. PEG 1.500 0,1%, 1% and 10%, Polysorbate 80 (0,04mg/ml) and Trometamol (1 mg/ml) were negative in all cases. TAB was positive only to Pfizer and Moderna vaccines but not to PEG or other excipients. Four additional woman with positive skin test were observed in the same period of time related to the first exposition to vaccines and only positive test were obtained with vaccines but not to PEG or other excipients studied. All of them sanitary workers affected by urticaria and/or angioedema and adenitis associated with cutaneous delayed reaction. More than 20 skin tests were negative as the same concentrations in other patients with suspected adverse reactions to vaccines or other drugs containing PEG. All negative patients were encouraged to receive the second dose and 10 did not have a recurrence of reaction. More than 10 BAT were also performed in cases and controls with negative results to PEG. A positive specific IgE to ethylene oxide was obtained. Conclusion: Different mechanisms of anaphylactic/anaphylactoid reaction are inferred from the results. In the most severe case, it was not possible to demonstrate an IgE mechanism involved. Skin test to vaccines involved were the most useful tool to diagnose hypersensitivity reactions. PEG was positive in one case, Ethylene oxide was positive in other case (associated with positive ID test to vaccines) and BAT in other two patients.