Anaphylaxis caused by vaccines

Abstract

Even though the SARS-CoV-2 pandemic represents a historical challenge, science has had an exponential development, and the current vaccination campaigns are proof of this. Unfortunately, along came misinformation and myths regarding their production and their adverse effects. For this reason, we have considered of utter importance to review anaphylaxis, one of the most feared vaccine adverse events. Anaphylaxis can be defined as a life-threatening acute and systemic allergic reaction, with a wide clinical spectrum, which can be explained by many immunological mechanisms, and whose diagnostic complexity demands the fulfillment of strict criteria. Though infrequent, any vaccine has the potential to trigger anaphylaxis. In the United States, for the new SARS-CoV-2 vaccines, rates from 1:200 000 (Pfizer-BioNTech) to 1:360 000 doses (Moderna) have been estimated. Vaccine adverse events can be mediated by hypersensitivity reactions, either allergic or not. Unlike a typical drug allergy, rarely is the active ingredient responsible for the reaction. Therefore, excipients must be considered during the approach to this problem. Vaccine associated anaphylaxis has to be referred to an allergist so as to guarantee the maximum benefit for the patient and improve the vaccines' security profile.