Background:

COVID‑19 vaccination is essential for the pandemic control. Adverse reactions after vaccination are common, although anaphylaxis is rare.

Objectives:

To characterize the immunoallergological reactions responsible for pre‑vaccination referral by Primary Care (PC), to analyze the impact of drug allergy on this referral, and to evaluate the vaccination outcome after risk stratification.

Methods:

Retrospective observational study including patients referred by PC to the Allergy & Clinical Immunology Department of a tertiary hospital to evaluate the risk of severe hypersensitivity reactions (HSR) after COVID‑19 vaccination, from January to June 2021. Risk stratification was carried out in accordance with the Allergy & Clinical Immunology Department’s protocol. Results: From a total of 733 patients referred by the CSP, 510 were admitted, 445 of which were evaluated, 369 (83%) females, mean age 66±13 years [20‑99 years], 122 (27%) atopic. The majority (n=349, 78%) were referred due to previous drug reactions, of whom 69 (15.5%) due to vaccine reactions. Nonsteroidal anti‑inflammatory drugs (n=97, 51%) and antibiotics (n=70, 36%) were the most reported drugs in suspected/confirmed HSRs. Drug reaction profile differed in low‑risk (61% with HSR, 39% anaphylaxis) and intermediate/high risk (92% with HSR, 65% anaphylaxis) patients. After risk assessment, 323 patients were referred for vaccination at the vaccination center, of whom 280 received at least one dose of the vaccine. Two patients had chronic urticaria worsening and one patient had a vasovagal reaction after the vaccine. 122 patients were vaccinated at the hospital, of whom 69 received one dose of the vaccine. Only two patients had mild skin reactions.

Conclusions:

Drug allergy was the main cause for pre‑vaccination risk assessment. Most patients were vaccinated at the vaccination center with no HSR. Risk assessment protocol was effective, with no significant reactions or cases of anaphylaxis.

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