Overview of COVID-19 vaccine adverse events

Since the beginning of the COVID-19 pandemic, researchers' efforts have focused on developing vaccines to reduce the risk of further global spread of the SARS-CoV-2 coronavirus infection. The research carried out allowed for the introduction, in an extremely short time, of preparations based on mRNA technology (Pfizer BioNTech and Moderna products), viral vector preparations (AstraZeneca AB and Janssen-Cilag International NV preparations), and protein-based preparations (Novavax CZ a.s. and Hipra Human Health, S.L.U. preparations). Clinical trials demonstrated the expected effectiveness of the vaccines, with a positive benefit-to-risk ratio allowing for their registration. However, as with other medicinal products, knowledge about the types and actual frequency of side effects is mostly acquired during the fourth, post-registration phase of drug monitoring, called pharmacovigilance, aimed at analysing the safety of commonly used medicinal products. It is now known that COVID-19 vaccines cause a number of non-specific (e.g. skin hypersensitivity reactions, headaches, muscle pain, fever after administration) and specific (e.g. "COVID arm", myocarditis and/or pericarditis, thrombocytopenic thrombosis) adverse reactions. It should be emphasised that the overall clinical evaluation of the vaccines remains positive, indicating their continued effectiveness (despite the still-present genetic variability of the virus) in protecting against severe course of the disease, hospitalisation, and death in high-risk patients with SARS-CoV-2 infection, while still maintaining an acceptable level of safety when used. This paper is a narrative review, summarising and systematising the most significant adverse events of the COVID-19 vaccines.