Evaluating vaccination dosing strategies for SARS-CoV-2 in patients at high-risk for allergic reactions: Insights from vaccination campaign.

Background: The COVID-19 pandemic significantly increased the demand for allergy consultations to evaluate the risk of hypersensitivity reactions in patients either before receiving their first dose of an anti-SARS-CoV-2 vaccine (Group 1) or following suspected allergic reactions after vaccination (Group 2).

Methods: We conducted a retrospective analysis of patients referred to the Immunology and Allergy Unit of the Azienda Ospedaliera Ordine Mauriziano in Turin, Italy, between December 2020 and December 2022. Risk assessment was performed according to Italian and European guidelines, and allergy skin tests were administered when necessary. Patient data were cross-referenced with the SIRVA platform (Regional Vaccination Management Information System) to assess vaccine eligibility, administration, and outcomes.

Results: A total of 1222 patients were evaluated (mean age: 52 years; female-to-male ratio 4:1). In Group 1 (n = 914), 137 patients (15%) underwent skin testing, of whom 15 (1.6%) tested positive. Vaccination was recommended for 899 patients (98%), though 184 (20%) did not proceed. Among those vaccinated, 679 (74%) received additional doses, with 48% receiving a third and 11% a fourth dose. In Group 2 (n = 308), 104 patients (33%) underwent skin testing, with 9 (8%) testing positive. Vaccination without restrictions was recommended for 299 patients (97%), but 45 patients (15%) did not proceed. Among the remaining, 262 (85%) received a second dose, 183 (59%) a third, and 29 (9%) a fourth dose. Overall, 1198 patients (98%) had no specific contraindications to vaccination. Only 5 patients (0.4%) were completely exempted from vaccination due to confirmed sensitivity to both polyethylene glycol (PEG) and polysorbate 80 (PS80). An alternative vaccine was recommended for 19 patients; 16 of them proceeded with vaccination and tolerated it without adverse effects.

Conclusions: Our findings demonstrate that the majority of high-risk allergic patients can safely receive anti-SARS-CoV-2 vaccines following allergological evaluation. The rate of confirmed excipient allergy was very low, and vaccine adherence was comparable to the general population. This is, to our knowledge, the first study to longitudinally assess the number and types of vaccine doses administered to high-risk allergic individuals.