Rationale
Messenger RNA (mRNA) based vaccines have proven to be a critical tool to combat the COVID-19 pandemic. While most patients tolerate them without adverse reactions, a small number have reactions concerning for mast cell degranulation. These reactions are poorly understood, and so there is little data to guide counseling on the safety of repeat vaccination.
Methods
The Washington University Division of Allergy and Immunology conducted a retrospective chart review of 82 patients referred with concern of adverse reaction following COVID-19 vaccination. We analyzed the history of these patients and the characteristics of their reactions, as well as if they tolerated repeat vaccination.
Results
Sixteen (20%) patients presented with delayed hives/angioedema after initial vaccination, without immediate symptoms. The average time to reaction was 43 hours. This group was predominantly female with an average age of 46 years. While 58% had a history of atopic disease, only 12.5% had a history of chronic hives and no patients had a history of mast cell activation. Nine had confirmed repeat vaccination with the same product and 8 did well or did not return to care. One patient experienced a self-limited recurrence of her reaction.
Conclusions
Delayed hives/angioedema following COVID-19 mRNA vaccination can occur. Even though these delayed reactions may be mast cell mediated, they appear to be idiosyncratic, possibly due to immune overactivation. Completion of the vaccine series as well as any future boosters is not definitively contraindicated.
525