Utility and Futility of Skin Testing to Address Concerns Surrounding mRNA COVID-19 Vaccine Reactions

Background The mechanism of COVID-19 vaccine hypersensitivity reactions is unknown. COVID19 vaccine excipient skin testing has been used in evaluation of these reactions, but its utility in predicting subsequent COVID-19 vaccine tolerance is also unknown. Objective To evaluate the utility of COVID-19 vaccine and vaccine excipient skin testing in both patients with an allergic reaction to their first mRNA COVID-19 vaccine dose and patients with a history of polyethylene glycol (PEG) allergy who have not yet received a COVID-19 vaccine dose. Methods In this multi-center, retrospective review, COVID-19 vaccine and/or vaccine excipient skin testing was performed in patients referred to one of three large tertiary academic institutions. Patient medical records were reviewed after skin testing to determine subsequent COVID-19 vaccine tolerance. Results 129 patients underwent skin testing, which was positive in 12 patients (9.3%). 101 patients received a COVID-19 vaccine after skin testing, which was tolerated in 90 patients (89.1%) with no allergic symptoms, including 5 of the 6 patients with positive skin testing who received a COVID-19 vaccine after skin testing. The remaining 11 patients experienced minor allergic symptoms following COVID-19 vaccination, none of which required treatment beyond antihistamines. Conclusion The low positivity rate of COVID-19 vaccine excipient skin testing and high rate of subsequent COVID-19 vaccine tolerance suggests a low utility of this method in evaluation of COVID-19 vaccine hypersensitivity reactions. Focus should shift to the use of existing vaccine allergy practice parameters, with consideration of graded dosing if necessary. Based on these results, strict avoidance of subsequent COVID-19 vaccination should be discouraged.