Eustachio Nettis

Coronavirus disease 2019 (COVID-19) was declared a global pandemic by the World Health Organization (WHO) in March 2020. Despite the availability of therapies and the adoption of security measures, the most effective method to fight COVID-19 remains the induction of immunity through vaccines. Scientific communities have developed several types of COVID-19 vaccines since the beginning of the pandemic, including those with innovative messenger RNA (mRNA) technology. Patients with a history of allergic reactions may have an increased risk of hypersensitivity reactions to COVID-19 vaccines. Therefore, it is important that these patients are evaluated by an allergist to help monitor immediate-type adverse reactions and identify what vaccine component may elicit an allergic reaction. Various strategies have been suggested to prevent hypersensitivity reactions, including performing skin tests or in vitro tests before vaccination in high-risk patients, administering a different vaccine for the second dose in subjects reporting adverse reactions to the first dose, fractional dosing, or pretreating with anti-immunoglobulin E (IgE) monoclonal antibody. The scope of this review is to evaluate, through current evidence available in the literature, the accuracy of skin testing to the excipients of COVID-19 vaccines, especially polyethylene glycol (PEG) and polysorbate, in predicting allergic reactions to vaccination, despite the existing discordance of data and approaches to the question from the various clinical experiences, as to permit the safe administration of COVID-19 vaccines to populations around the globe.