SARS-CoV-2 variant of concern

Before being allocated to this category, an emerging variant may have been labeled a variant of interest (VOI), or in some countries a variant under investigation (VUI). During or after fuller assessment as a variant of concern the variant is typically assigned to a lineage in the Pango nomenclature system and to clades in the Nextstrain and GISAID 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. This was principally for reasons of transmissibility and virulence, and also with regard to the possible emergence of escape mutations.

Criteria

Several national and international health organisations (e.g. Centers for Disease Control and Prevention (CDC) (US), Public Health England (PHE) and the COVID-19 Genomics UK Consortium for the UK, and the Canadian COVID Genomics Network (CanCOGeN)) use some or all of the following criteria to assess variants:

• Increased transmissibility
• Increased morbidity
• Increased mortality
• Increased risk of "long COVID"
• Ability to evade detection by diagnostic tests
• Decreased susceptibility to antiviral drugs (if and when such drugs are available)
• Decreased susceptibility to neutralizing antibodies, either therapeutic (e.g., convalescent plasma or monoclonal antibodies) or in laboratory experiments
• Ability to evade natural immunity (e.g., causing reinfections)
• Ability to infect vaccinated individuals
• Increased risk of particular conditions such as multisystem inflammatory syndrome or long-haul COVID.
• Increased affinity for particular demographic or clinical groups, such as children or immunocompromised individuals.

Variants that appear to meet one or more of these criteria may be labeled "variants of interest" or "variants under investigation" ('VUI') pending verification and validation of these properties. Once validated, variants of interest /VUI may be renamed "variants of concern" by monitoring organizations, such as the CDC. A related category is "variant of high consequence", used by the CDC if there is clear evidence that the effectiveness of prevention or intervention measures for a particular variant is substantially reduced.