Skin testing for exploration of hypersensitivity to SARS-Cov- 2 vaccines or its excipients: A retrospective monocentric cohort of pediatric and adult patients

ABSTRACT

Background: National guidelines recommend that patients with high risk of allergic reactions to COVID-19 vaccinations must undergo allergological evaluation before authorizing vaccination. To date, allergological testing to COVID-19 vaccines and its excipients is not standardized. There is a need to provide more data on skin testing (ST) to COVID-19 vaccines. In this study, we aimed to evaluate the performance of skin testing with SARS-CoV- 2 vaccines and their excipients in our cohort of adult and pediatric patients. Method(s) All patients evaluated for a suspicion of allergy to any of the vaccine components (polyethylene glycols (PEGs) and polysorbate (PS)), or with a history of immediate or delayed reaction to a first injection of an mRNA vaccine were included. Evaluated patients received the following ST *PEG 400 and 4000 (100 mg/ml), prick (PT) 11 and intradermal tests (IDR) 1100,000, 110,000, 11000, 1100, 110. *PS80 (0.4 mg/ml), PT 11, IDR 11000, 1100, 110. *Tozinameran (Comirnaty) vaccine (30 mug/0.3 ml), PT 11 and IDR 110. ST readings were performed after 20 minutes for immediate reaction and 24 hours for delayed reaction. Patients were systematically contacted by phone after vaccination to assess side effects including anaphylaxis. Result(s) Between February 1st and October 31st 2021, 83 patients underwent allergological testing, with a majority of female (83.1%). Age (mean +/- SD) was 51 +/- 18 years old (yo) (range 12-91 yo). Among those patients, 35 were tested following a reaction to the SARS-CoV- 2 vaccine and 48 for a suspected allergy to an excipient. No patients reported anaphylactic reaction after a COVID vaccine. Among them, 13 had positive ST (1 patient to PS80 IDR, 1 patient to PS80 PT and vaccine IDR, 11 patients to vaccine 5 delayed IDR, 5 immediate IDR, 1 doubtful IDR). Eleven patients were vaccinated, well tolerated. We have no information about COVID vaccination for 2 patients. Out of the 70 patients with negative ST, 5 chose not to be vaccinated and 54 (77.1%) got vaccinated (11 (15.7%) did not respond to the phone call). No anaphylactic reactions were reported. Conclusion(s) In our cohort, vaccinations do not lead to hypersensitivity reactions, regardless of test results. We did not find real IgE mediated allergy. Vaccine IDR seemed too irritating and did not contribute to the diagnosis of vaccine hypersensitivity. The clinical context and skin tests results are helpful in authorizing vaccination.