SARS-CoV-2 Variant Classifications and Definitions

Key Points:

Genetic variants of SARS-CoV-2 have been emerging and circulating around the world throughout the COVID-19 pandemic.
Viral mutations and variants in the United States are routinely monitored through sequence-based surveillance, laboratory studies, and epidemiological investigations.
A US government interagency group developed a Variant Classification scheme that defines three classes of SARS-CoV-2 variants:
The B.1.526, B.1.526.1, B.1.525, B.1.617, B.1.617.1, B.1.617.2, B.1.617.3, and P.2 variants circulating in the United States are classified as variants of interest.
The B.1.1.7, B.1.351, P.1, B.1.427, and B.1.429 variants circulating in the United States are classified as variants of concern.
To date, no variants of high consequence have been identified in the United States.
In laboratory studies, specific monoclonal antibody treatments may be less effective for treating cases of COVID-19 caused by variants with the L452R or E484K substitution in the spike protein.
- L452R is present in B.1.526.1, B.1.427, and B.1.429.
- E484K is present in B.1.525, P.2, P.1, and B.1.351, but only some strains of B.1.526 and B.1.1.7.

Viruses constantly change through mutation. A variant has one or more mutations that differentiate it from other variants in circulation. As expected, multiple variants of SARS-CoV-2 have been documented in the United States and globally throughout this pandemic. To inform local outbreak investigations and understand national trends, scientists compare genetic differences between viruses to identify variants and how they are related to each other.