Desensitization protocol for anti-SARS- CoV- 2 vaccines in allergic patients: A case series

ABSTRACT

Background: Vaccination has proven to be the best viable tool for preventing the spread of SarsCov2 infection. The fear of adverse events represents one of the limits of this vaccination campaign. As Allergists, we had a fundamental role evaluating the allergological risks and performing specific tests. The only absolute contraindication to SARS-CoV- 2 vaccination is hypersensitivity to its components. When an individual is allergic to an indispensable medication, it is possible to resort to desensitization. Given the lack of a standardized scheme, the aim of our study is to propose a desensitization protocol for anti-SARS- CoV- 2 vaccines. Method(s) The desensitization protocol we developed consists in the fractioned administration of the entire vaccine dose into 5 separate injections of increasing quantity, through a 2-hour period. Premedication with antihistamines and chromones was administrated. Between January 2021 and January 2022, 23 patients referred to our Unit were deemed with a high risk of hypersensitivity reactions to the vaccines and underwent the desensitization protocol. We here describe 23 consecutive cases of patients who underwent desensitization to anti-SARS- CoV- 2 vaccine. Result(s) 4/23 had positive allergy skin test to Polysorbate and underwent desensitization for their entire vaccination cycle. 19/23 had a previous hypersensitivity reaction to an anti-SARS- CoV- 2 vaccine (18 after the first dose and 1 after the second one). Among 4 patients with sensitization to Polysorbate none developed hypersensitivity reactions after fractionated administration of BNT162b2 vaccine. Among 19 patients that underwent desensitization because of hypersensitivity reactions after I or II dose of vaccine, 15 experienced a reaction following vaccination with BNT162b2, 4 with mRNA-1273 and 4 with ChAdOx1-S recombinant. Furthermore, we categorized their reactions according to WAO score per systemic reactions 15/19 (79%) grade1, 2/19 (10.5%) grade2, 2/19 (10.5%) grade3. No severe late hypersensitivity reactions were observed. All but one of this 19 patients had no hypersensitivity reactions after vaccination through the desensitization protocol. 1 patient experienced anaphylaxis during desensitization with BNT162b2 vaccine (WAO grade4). No late hypersensitivity reactions were observed. Overall, 22/23 (95.6%) patients that underwent anti-SARS- CoV- 2 vaccination through the desensitization protocol did not experience hypersensitivity reactions. Conclusion(s) Our results suggest that desensitization can be implemented to extend the vaccination to currently ineligible individuals. Larger studies are needed to prove the safety and efficacy of this approach.