REVISITING HYPERSENSITIVITY REACTIONS TO THE MRNA COVID-19 VACCINE: TOLERANCE AFTER PREVIOUS HISTORY OF ANAPHYLAXIS

INTRODUCTION: Based on the current evolving knowledge regarding potential mechanisms of immediate reactions to the COVID-19 vaccine, we wanted to study the clinical tolerance of subsequent mRNA vaccination in patients with reported anaphylaxis to either the Moderna® mRNA-1273 or Pfizer-BioNTech® BNT162b2 vaccine. METHODS: We revaluated a subgroup of 6 patients that reported anaphylaxis to the first COVID-19 vaccine (5/6 – level 2 Brighton criteria classification and 1/6 level 4), as part of a large prospective COVID-19 Vaccine study (ARCOV). Among these, PEG skin test was positive for 2/6 patients. Patient had safely received their second dose using a desensitization protocol and were offered a booster dose of the Pfizer-BioNTech COVID-19 vaccine using a two-step blinded placebo-controlled challenge with a 1-hour observation period in a monitored setting. RESULTS: All 6 patients were females with a history of atopy and anaphylaxis to other agents. One patient was premedicated with prednisone and antihistamine. One patient refused, one tolerated a single dose challenge in the community, 3 tolerated a 2-step challenge and 2 presented mild isolated skin reactions (one patient despite the premedication). These reactions were hives and itchiness and were managed with oral antihistamines. One patient reacted to placebo with pruritis, sensation of throat closure, and dizziness but following reassurance safely completed the open challenge. CONCLUSION: Our results underline the safety of the mRNA COVID-19 booster vaccine in a monitored setting for patients with a previous history of anaphylaxis. Large scale studies are required to better understand the underlying mechanisms of the COVID-19 vaccine reported reactions.