U.S. government classifies threat levels of SARS-CoV-2 variants

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The number of SARS-CoV-2 variants with enhanced transmissibility and resistance to antibodies is increasing, prompting the U.S. government to issue guidance on how to classify them.

The criteria divide variants into three categories including the following:

Variant of interest: This virus type has genetic markers that have been linked to a potentially increased risk. Examples include mutations that could change how the virus enters cells and responds to antibodies from vaccination or infection. Such a virus could also potentially enhance transmissibility or disease severity.
Variant of concern: This class includes variants with evidence of increased transmissibility, severe disease or reduction in neutralization by antibodies from infection or vaccination. Such a variant may also pose a higher risk of eluding testing. See the table below for examples.
Variant of high consequence: This category poses the most significant risk. A variant of high consequence has a demonstrable ability to evade prevention measures or medical countermeasures. Such a variant could potentially elude vaccines or medical treatments. No SARS-CoV-2 variants currently meet this threshold.

To classify a SARS-CoV-2 “variant of concern” requires significant evidence of its increased risk.

Conversely, the threshold for classifying a “variant of interest” is relatively low.

To classify variants, CDC will collaborate with the newly formed SARS-CoV-2 Interagency Group (SIG). That group contains experts from FDA, NIH and other government agencies.

“The SIG focuses on rapid characterization of the emerging [variants of concern] and actively monitors their potential influence on critical SARS-CoV-2 countermeasures including diagnostics, therapeutics, and vaccines,” explained in a JAMA article coauthored by CDC director Rochelle Walensky.

Variant of Concern Name	First Detected	Known Attributes
B.1.1.7	United Kingdom	Roughly 50% increased transmissibility. Suspected to increase disease severity. This variant has minimal impact on authorized monoclonal antibody therapeutics. Currently available vaccines continue to be effective against this variant.
P.1	Japan/ Brazil	Possibly more transmissible. One preprint study estimated this variant was between 1.4 and 2.2 times more transmissible than the original coronavirus strain. Moderate impact on authorized monoclonal antibody therapeutics. Reduced neutralization by convalescent and post-vaccination sera.
B.1.351	South Africa	Roughly 50% increased transmissibility. Moderate impact on authorized EUA monoclonal antibody therapeutics. Moderate reduction on neutralization by convalescent and post-vaccination sera.
B.1.427	California	Roughly 20% increased transmissibility. Significant impact on neutralization by some authorized therapeutics. Moderate reduction in neutralization using convalescent and post-vaccination sera.
B.1.429	California	Roughly 20% increased transmissibility. Significant impact on neutralization by some, but not all, COVID-19 therapeutics. Moderate reduction in neutralization using convalescent and post-vaccination sera