ABSTRACT
Background: COVID-19 vaccines are being administered all over the world, but information is lacking about the frequency and type of allergic reactions associated to these new vaccines. Method: Retrospective study of health care professionals (HCP) from our hospital who received COVID 19 vaccine Comirnaty, between 29/12/2020 and 20/2/2021. We reviewed clinical data, particularly the immediate reactions after the administration (<6h), skin tests (ST) and graded vaccine administration. Following national guidelines, all HCP with previous history of food, drug or hymenoptera venom allergy or idiopathic anaphylaxis (IA) were first evaluated by an allergist. Vaccination was postponed if HCP had previous history of IA and/or recurrent anaphylaxis (RA), severe allergic reactions to vaccines and mast cell activation syndromes. ST to the vaccine (prick and intradermal) were performed in HCP with IA and/ or RA, severe allergic reactions to vaccines and HCP with immediate reactions to the 1st dose. Graded administration of the vaccine (0.1+0.2cc after 30') was performed in the postponed HCP and the ones with immediate reactions to the 1st dose. Results: From 3073 HCP who received the vaccine, 74.2% were female, mean age 40.2 years-old ± 13.4, 316 (10.3%) were evaluated by an allergist and 4 (1.3%) postponed the administration and performed allergy investigation. 2955 HCP (97%) were able to receive the 2 doses of the vaccine. 118 employees received only one dose: 98 had COVID-19 meanwhile, 7 got pregnant, 13 due to other conditions. Adverse reactions to the vaccine with possible hypersensitivity mechanisms, occurred in 17 (0.6%) HCP, 12 on the 1st dose and 5 on the 2nd dose. Observed reactions were 6 (0.2%) urticaria, 5 (0.16%) pruritus with or without flushing, 2 (0.07%) anaphylaxis (mild), 2 (0.07%) flushing and hoarseness, 1 (0.03%) flushing and nausea and 1 (0.03%) asthma exacerbation. ST with the vaccine were performed in 4 HCP, all negative in the immediate reading and 1 positive in non-immediate reading. 7 HCP undertook the graded administration with the vaccine: 6 tolerated, but one reproduced the immediate urticaria with 0.1cc of the vaccine (0.03% vaccine allergy). Conclusion: In the evaluated sample, suspicious allergic reactions to COVID19 vaccine Commirnaty were rare and allergy was only confirmed in one HCP. The allergist initial evaluation was essential for a safe risk stratification and permitted the non-exclusion of a considerable number of HCP from the vaccination program.