SARS-CoV-2 variant of concern

The term variant of concern (VOC) for SARS-CoV-2, which causes COVID-19, is a category used for variants of the virus where mutations in their spike protein receptor binding domain (RBD) substantially increase binding affinity (e.g., N501Y) in RBD-hACE2 complex (genetic data), while also being linked to rapid spread in human populations (epidemiological data).^[1]

Before being allocated to this category, an emerging variant may have been labeled a variant of interest (VOI),^[2] or in some countries a variant under investigation (VUI).^[3] During or after fuller assessment as a variant of concern the variant is typically assigned to a lineage in the Pango nomenclature system^[4] and to clades in the Nextstrain^[5] and GISAID^[6] systems.

During the COVID-19 pandemic, the SARS-CoV-2 virus has been observed to mutate, with certain combinations of specific point mutations proving to be more concerning than others.^[7] This was principally for reasons of transmissibility and virulence, and also with regard to the possible emergence of escape mutations.

As of May 2024, the Delta and the Omicron variants are designated as circulating variants of concern by the World Health Organization.