The Variation of SARS-CoV-2 and Advanced Research on Current Vaccines

Over the past 2 years, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) caused the coronavirus disease 2019 (COVID-19) and rapidly spread worldwide. In the process of evolution, new mutations of SARS-CoV-2 began to appear to be more adaptable to the diverse changes of various cellular environments and hosts. Generally, the emerging SARS-CoV-2 variants are characterized by high infectivity, augmented virulence, and fast transmissibility, posing a serious threat to the prevention and control of the global epidemic. At present, there is a paucity of effective measurements to cure COVID-19. It is extremely crucial to develop vaccines against SARS-CoV-2 and emerging variants to enhance individual immunity, but it is not yet known whether they are approved by the authority. Therefore, we systematically reviewed the main characteristics of the emerging various variants of SARS-CoV-2, including their distribution, mutations, transmissibility, severity, and susceptibility to immune responses, especially the Delta variant and the new emerging Omicron variant. Furthermore, we overviewed the suitable crowd, the efficacy, and adverse events (AEs) of current vaccines.