Anaphylaxis and allergic reactions to COVID‐19 vaccines: A narrative review of characteristics and potential obstacles on achieving herd immunity

BACKGROUND AND AIMS: Coronavirus disease 2019 (COVID‐19) is a highly contagious infection, and new variants of its causative virus continue to emerge all around the world. Meanwhile, mass vaccination represents a highly effective measure to reduce the disease burden. Not only do vaccines immunize individuals, but they also protect the entire population through achieving herd immunity. They are composed of various ingredients, some of which may induce hypersensitivity reactions, namely anaphylaxis and cutaneous allergic reactions. This review aims to provide an explicit overview of the pathophysiology, suspected responsible components, and management of COVID‐19 vaccine‐induced allergic reactions, and their effect on acquiring herd immunity. METHODS: To perform this narrative review, a comprehensive literature search based on our selected terms was conducted in online databases of PubMed/Medline and Google Scholar for finding the relevant studies published from 2019 to 2022. RESULTS: COVID‐19 vaccines introduce several advantages that outweigh their potential risks, such as allergic reactions. Allergic reactions are mainly attributed to polyethylene glycol and polysorbate excipients that can provoke IgE‐mediated reactions and hypersensitivity reactions. These reactions should be managed properly to avoid having serious sequelae. CONCLUSION: It is of great importance to immediately recognize and manage vaccine hypersensitivity reactions, especially anaphylaxis, to avoid allergic patients being excluded from the vaccination program, and more importantly, to stop the spreading of unfounded vaccine hesitancy leading to delayed herd immunity.