CDC Establishes New Threat Levels for COVID-19 Variants

In an effort to outline what is known about the circulating COVID-19 variants, the Centers for Disease Control and Prevention (CDC), along with several other government agencies, has established a classification system for variants of SARS-CoV-2, the virus that causes COVID-19.

The classification system breaks variants into different categories based on threat. Variants may be moved to different categories as scientific evidence develops. The agency drew inspiration from the World Health Organization (WHO), which also classifies variants by how they can impact the public. However, the CDC stresses that its classifications may vary from those of the WHO “since the importance of variants may differ by location.”

The system was developed as part of the SARS-CoV-2 Interagency Group (SIG), a group designed to improve coordination between U.S. government health organizations. The group is specifically focused on characterizing emerging SARS-CoV-2 variants and monitoring their potential impact on vaccines, treatments, and diagnostics.

The classification system “is useful for the general public to understand that the variants are spreading,” Richard Watkins, MD, an infectious disease specialist and a professor of internal medicine at the Northeast Ohio Medical University, tells Verywell. “This isn’t the time to let our guard down in terms of mitigation efforts—mask-wearing, avoiding crowds, etc.”

Variant Classifications

A variant has one or more mutations that differentiate it from other variants of a virus in circulation. Several variants of SARS-CoV-2 have been detected, both across the world and in the U.S.

The CDC specifically breaks SARS-CoV-2 variants into three groups:

• Variants of interest
• Variants of concern
• Variants of high consequence

John Sellick, DO, an infectious disease expert and professor of medicine at the University at Buffalo/SUNY, tells Verywell that the information is “useful, even for professionals. There have been different systems and classifications that are used. It’s helpful to just have one."

Variants of Interest

Variants of interest are those with genetic markers that affect how well the virus binds to cells. They also may reduce the effectiveness of antibodies developed against SARS-CoV-2 from a previous infection or vaccination.

COVID-19 treatments may not work as well against these variants and they may be more infectious and able to cause worse disease than other strains. There is evidence that these variants increase the number of cases or cause outbreak clusters, but there is limited spread in the U.S. or other countries.

Variants of interest may require enhanced surveillance and investigations to see how easily they spread, the risk of reinfection, and whether the vaccines protect against them.

Currently, the CDC lists the following as variants of interest in the U.S.:

• B.1.526, first detected in New York
• B.1.525, first detected in New York
• P.2, first detected in Brazil

Variants of Concern

Variants of concern are more likely to spread widely due to higher transmissibility. These variants may also cause a more severe course of the disease (either through hospitalizations or deaths).

These variants may also lead to widespread interference with diagnostic testing and resistance to one or more types of treatment. Evidence suggests that antibodies from natural infection or vaccination aren’t as effective against these strains.

The CDC specifically lists the following as variants of concern:

• B.1.1.7, first detected in the U.K.
• P.1, first detected in Japan in travelers from Brazil
• B.1.351, first detected in South Africa
• B.1.427, first detected in California
• B.1.429, first detected in California

Variants of High Consequence

A strain is deemed a variant of high consequence when there is clear evidence that prevention measures or medical countermeasures do not work as well on curbing the virus compared to other variants.

Variants of high consequence are not easily diagnosed, significantly reduce the effectiveness of vaccines or have a high number of vaccine breakthrough cases, and aren’t easily treated. They also cause a more severe course of disease and hospitalizations.

These high consequence variants require public health officials to declare a Public Health Emergency of International Concern (PHEIC) if it hasn’t already been declared. New strategies to prevent or contain transmission must also be developed.

The CDC has not named any SARS-CoV-2 variants as variants of high consequence.

Infectious disease expert Amesh A. Adalja, MD, senior scholar at the Johns Hopkins Center for Health Security in Maryland, tells Verywell that he agrees with the CDC’s assessments of the existing variants. “To me, a high consequence variant would be one for which a vaccine was unable to prevent serious disease, hospitalization, and death,” he says. “This doesn’t seem to be the case for any of the variants of concern.”

As the U.S. continues to track variants across the country, Adalja stresses the importance of vaccination in fighting back against variants. “In countries that can vaccinate quickly, the variants are much more manageable and less concerning,” he says. “In countries in which vaccination is faltering, the variants could become very important.”

The information in this article is current as of the date listed, which means newer information may be available when you read this. For the most recent updates on COVID-19, visit our coronavirus news page.