Resolution of Patient's Anaphylaxis to the Moderna COVID-19 Vaccine by Desensitization.

Introduction: Management of patients with rare anaphylaxis to COVID-19 vaccines creates a challenge. Desensitization to medications and vaccines has proven to be effective in managing anaphylactic reactions in selected individuals with a high benefit-to-risk ratio. A previous report described the successful administration of the Moderna modified messenger RNA (MmRNA) COVID-19 vaccine via a graded dose protocol to a patient with previous anaphylaxis to the MmRNA vaccine. Our report describes successful desensitization to the MmRNA vaccine followed by administration of the full dose MmRNA vaccine.

Case presentation: A patient with a history of chronic allergies and anaphylaxis due to insect sting venom reported anaphylaxis after her first dose of the MmRNA vaccine, for which she was premedicated. She was subsequently clinically diagnosed with anaphylaxis to skin testing of the MmRNA vaccine-meeting Brighton's criteria for level 1 certainty of diagnosis-and underwent a desensitization protocol to the vaccine. After the desensitization protocol, the patient was administered the full second dose of the MmRNA vaccine via intramuscular injection, without systemic allergic reactions, and with elicitation of an immunological response.

Conclusion: This severely allergic patient developed 2 separate anaphylactic reactions to the MmRNA vaccine despite being treated with omalizumab. The patient was then desensitized to the MmRNA vaccine and was subsequently administered the full second dose of MmRNA vaccine via intramuscular injection without systemic allergic reactions and with elicitation of an immunological response. Our patient's case illustrates the ability to desensitize patients who desire administration of the MmRNA vaccine, but are unlikely to prevent anaphylaxis with premedication.