SARS-CoV-2 Variants: How Many and How Dangerous?

March 30, 2021

The CDC defines 3 classes of SARS-CoV-2 variants: Variants of interest, of concern, and of high consequence. Find out more about the 8 variants now being closely observed.

The Centers for Disease Control and Prevention (CDC) classify SARS-CoV-2 variants in circulation in the United States as variants of interest, variants of concern, and variants of high consequence.

Each classification describes and identifies the variant in terms of its impact on critical SARS-CoV-2 countermeasures including vaccines, therapeutics and diagnostics. Variants of interest in the US right now include the 2 identified in New York at the end of 2020; variants of concern to the CDC include those from the UK and South Africa.

The following slides summarize the most salient details on 8 SARS-CoV-2 variants of interest and concern to the CDC as of March 30, 2021. The CDC data are updated regularly.

SARS-CoV-2 Variants of Interest have genetic markers that have been associated with, among other traits, changes to receptor binding and reduced efficacy of treatments.

Possible Attributes of SARS-CoV-2 Variants of Interest. Among the attributes are specific genetic markers that are predicted to affect transmission, diagnostics, therapeutics, or immune escape.

Public Health Response to SARS-CoV-2 Variants of Interest. These could include epidemiologic investigations to asses how easily the virus spreads, disease severity, risk of reinfection, and whether or not currently authorized vaccines offer protection.

Current SARS-CoV-2 Variants of Interest. B.1.526 and B.1.525, both detected in New York at the end of 2020.

Current SARS-CoV-2 Variants of Interest. P.2 was first detected in Brazil in Spring of 2020.

SARS-CoV-2 Variants of Concern. These variants are associated with increased risk of transmission, more severe disease, reduced efficacy of treatments and vaccines, and failure of diagnostic detection.

Possible Attributes of SARS-CoV-2 Variants of Concern. Evidence of impact on diagnostics, treatments, vaccines including widespread interference with diagnostic test targets and evidence of substantially increased resistance to one or more class of therapies or of significantly decreased neutralization by antibodies generated during previous infection or vaccination.

Note: Each class of variant includes the possible attributes of lower classes.

Public Health Response to SARS-CoV-2 Variants of Concern. Among responses that may be required are notification of the World Health Organization under the International Health Regulations, reporting to the CDC, increased testing, and research to determine whether existing vaccines and treatments are effective against the strain.

SARS-CoV-2 Variants of Concern. The B.1.1.7 variant was first detected in the UK and among the KNOWN attributes of the variant are its ~50% greater transmissibility and likely increased severity based on current information on hospitalizations and case fatality rates.

SARS-CoV-2 Variants of Concern. The B.1.351 variant, first detected in South Africa, also is associated with ~50% greater transmissibility; it is observed to have moderate impact on neutralization by EUA mAb therapeutics and to exert moderate reduction on neutralization by convalescent &post-vaccination sera.

SARS-CoV-2 Variants of Concern. The B.1.427 and B.2.429 variants, both detected originally in California, demonstrate ~20% greater transmissibility and have a significant impact on neutralization by EUA mAb therapeutics.

SARS-CoV-2 Variants of Concern. The P.1 variant was first detected in Japan and Brazil and has been found to have a moderate impact on neutralization by EUA mAb treatments and reduced neutralization by convalescent & post-vaccination sera.

SARS-CoV-2 Variants of High Consequence. For a variant of high consequence there is clear evidence that the effectiveness of prevention measures or medical countermeasures is/are significantly reduced relative to previously circulating variants.

Possible Attributes of SARS-CoV-2 Variants of High Consequence. Such a variant has profound impact on medical countermeasures including: demonstrated failure of diagnostics, and 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.

Note: Each class of variant includes the possible attributes of lower classes.

Public Health Response to SARS-CoV-2 Variants of High Consequence. Treatments and vaccines would need to be updated.

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