ABSTRACT
Background: During the initial rollout of COVID-19 vaccination in Singapore, the Ministry of Health (MOH) issued recommendations that patients with a history of any previous vaccine allergy be referred to an allergist for further review on suitability to proceed with mRNA-based COVID-19 vaccines. We review the evaluation of these patients with suspected vaccine allergies prior to receiving mRNA-based COVID-19 vaccines. Method(s): Between 8 April and 22 September 2021, 304 patients were evaluated prior to receiving the COVID-19 vaccinations. Of these, 63 (20.7%) patients with suspected immediate hypersensitivity reactions to non-COVID polysorbate-containing vaccines proceeded to have skin prick test (SPT) and Intradermal test (IDT) to polyethylene glycol (PEG)-3350, polysorbate 80 and polysorbate 20 containing products. Another 62 (20.4%) who reported delayed hypersensitivity reactions to polysorbate-containing vaccines proceeded to have direct inoculation (DI) of the Pfizer BNT162b2 vaccine under the supervision of an allergist. The remaining 242 (76.6%) finally assessed not allergic polysorbate-or tolerated previous non-polysorbate- containing vaccines were recommended to proceed with COVID-19 vaccinations at the community vaccination sites. 99 patients in the SPT/IDT and DI group completed a questionnaire-based survey to report any post vaccination reactions. (Figure 1) Results: Of 63 patients who underwent SPT/IDT, 2 (3.2%) with equivocal IDT tolerated both doses of the BNT162b2 vaccine without major allergic reactions. 61 (6.8%) patients with negative SPT/IDT and 62 (100%) in the DI group completed both doses of BNT162b2 vaccination without major reactions. Among those who completed the questionnaire survey, 13 (13%) reported reactions including non-specific rashes and mild urticaria/angioedema post first dose vaccine. All subsequently completed the second dose of the BNT162b2 vaccine following allergist review;with 8 (61.5%) reporting similar mild skin reactions. Conclusion(s): Majority of those with suspected reactions to polysorbate containing vaccines are able to tolerate the BNT162n2 vaccine which contains PEG-2000. Skin tests prior to mRNA COVID-19 vaccination is unnecessary. Those who report mild potentially allergic reactions after the first dose are able to tolerate the second dose of the BNT162b2 vaccine.