Molecular variants of SARS‑CoV‑2: antigenic properties and current vaccine efficacy

An ongoing pandemic of newly emerged SARS-CoV-2 has puzzled many scientists and health care policymakers around
the globe. The appearance of the virus was accompanied by several distinct antigenic changes, specifically spike protein
which is a key element for host cell entry of virus and major target of currently developing vaccines. Some of these mutations
enable the virus to attach to receptors more firmly and easily. Moreover, a growing number of trials are demonstrating
higher transmissibility and, in some of them, potentially more serious forms of illness related to novel variants. Some of
these lineages, especially the Beta variant of concern, were reported to diminish the neutralizing activity of monoclonal and
polyclonal antibodies present in both convalescent and vaccine sera. This could imply that these independently emerged
variants could make antiviral strategies prone to serious threats. The rapid changes in the mutational profile of new clades,
especially escape mutations, suggest the convergent evolution of the virus due to immune pressure. Nevertheless, great
international efforts have been dedicated to producing efficacious vaccines with cutting-edge technologies. Despite the
partial decrease in vaccines efficacy against worrisome clades, most current vaccines are still effective at preventing mild to
severe forms of disease and hospital admission or death due to coronavirus disease 2019 (COVID-19). Here, we summarize
existing evidence about newly emerged variants of SARS-CoV-2 and, notably, how well vaccines work against targeting new
variants and modifications of highly flexible mRNA vaccines that might be required in the future.