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ACEP COVID-19 Field Guide

Table of Contents

Characteristics of COVID-19 Variants and Mutants

Characteristics of COVID-19 Variants and Mutants

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. In collaboration with the SARS-CoV-2 Interagency Group (SIG), CDC established a classification scheme for variants of SARS-CoV-2:

  • Variants of Interest
  • Variants of Concern
  • Variants of High Consequence

Variants of Interest

A variant with specific genetic markers that have been associated with changes to receptor binding, reduced neutralization by antibodies generated against previous infection or vaccination, reduced efficacy of treatments, potential diagnostic impact, or predicted increase in transmissibility or disease severity. Possible attributes of a variant of interest:

  • Specific genetic markers that are predicted to affect transmission, diagnostics, therapeutics, or immune escape
  • Evidence that demonstrates it is the cause of an increased proportion of cases or unique outbreak clusters
  • Limited prevalence or expansion in the US or in other countries

Variants of Concern

A variant for which there is evidence of an increase in transmissibility, more severe disease (increased hospitalizations or deaths), significant reduction in neutralization by antibodies generated during previous infection or vaccination, reduced effectiveness of treatments or vaccines, or diagnostic detection failures. Possible attributes of a variant of concern (in addition to the possible attributes of a variant of interest): 

  • Evidence of impact on diagnostics, treatments, and vaccines
    • Widespread interference with diagnostic test targets
    • Evidence of substantially increased resistance to one or more class of therapies
    • Evidence of significant decreased neutralization by antibodies generated during previous infection or vaccination
    • Evidence of reduced vaccine-induced protection from severe disease
  • Evidence of increased transmissibility
  • Evidence of increased disease severity

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.

Variants of High Consequence

A variant of high consequence has clear evidence that prevention measures or medical countermeasures (MCMs) have significantly reduced effectiveness relative to previously circulating variants. Possible attributes of a variant of high consequence (In addition to the possible attributes of a variant of concern):

  • Impact on Medical Countermeasures (MCM)
    • Demonstrated failure of diagnostics
    • Evidence to suggest a significant reduction in vaccine effectiveness, a disproportionately high number of vaccine breakthrough cases, or very low vaccine-induced protection against severe disease
    • Significantly reduced susceptibility to multiple EUA or approved therapeutics
    • More severe clinical disease and increased hospitalizations

Currently there are no SARS-CoV-2 variants that rise to the level of high consequence.

Additional information can be found on the webpage for the CDC’s SARS-CoV-2 Variant Classifications and the National Genomic Surveillance Dashboard.

Table Current variants in the United States.

Characteristics of COVID-19 Variants and Mutations.jpg

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