What Is the B.1.351 Variant?

What to know about this COVID-19 mutation

Since the start of the COVID-19 pandemic, multiple variants of the virus have developed, including the B.1.351 variant—which was initially discovered in South Africa in December 2020.

Virus Background

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Where B.1.351 Has Spread

The B.1.351 variant has now spread to at least 82 countries worldwide, including the United States.

Spread in the United States

The B.1.351 variant was initially found in the United States in January 2021, with the first case found in the state of Washington. There have been less than 500 total confirmed cases of the B.1.351 variant in the United States; it has been documented in 32 states.

Why Do Viruses Mutate?

It is common for all viruses to mutate. When a virus enters the body, it begins to make copies of itself.

Sometimes during this process, mistakes (mutations) are made in the copies, which can make it easier for the virus to invade the cell. When this same mutation continues to further copy itself, a variant of the virus forms.

Is B.1.351 More Contagious?

The B.1.351 variant is thought to be more contagious than the original COVID-19 virus. The Centers for Disease Control and Prevention (CDC) estimates a 50% increased transmission rate of COVID-19 from the B.1.351 variant.

The infectiousness of a virus is measured by an R number, or the number of people an infected person will give the virus to. For example, if the R is 1, an infected person is likely to give it to one other person; an R of 5 means an infected person is going to transmit it to five other people.

Preventing Transmission

Precautions to prevent the transmission of the B.1.351 variant are the same as for the original COVID-19 virus and should continue to be followed. These precautions include:

  • Staying 6 feet apart from others who don’t live in your household
  • Wearing a mask that covers your mouth and nose
  • Good hand hygiene by washing hands often or using hand sanitizer  

If you are fully vaccinated, the CDC has released new guidelines that say it is safe to gather indoors with other fully vaccinated people and to not wear a mask when outdoors, unless it is a crowded setting or venue.

Risk of Reinfection

It is possible that the B.1.351 variant can cause reinfection. Studies have shown that natural immunity from previous COVID-19 infection does not protect well against this variant, but there is limited data to support the risk of reinfection at this time.

Is B.1.351 More Severe?

This is currently being studied, but evidence comparing COVID-19 hospitalization and severity from the original COVID-19 virus versus the B.1.351 variant in South Africa showed that there was an increase in mortality rate in those with the B.1.351 variant.

This was a small study, and further research is needed to confirm these findings, as other studies have not found this variant to cause more severe COVID-19.

Recent studies also uncovered that specific monoclonal antibody treatments may be less effective for treating cases of COVID-19 caused by the B.1.351 variant.

Will Vaccines Work Against B.1.351?

The World Health Organization (WHO) has reported that the B.1.351 variant does cause a decrease in the effectiveness of vaccines.

Regarding the Pfizer and Moderna vaccines, the studies have had various outcomes on the total reduction of effectiveness, from very little reduction to more substantial reduction. The Johnson & Johnson vaccine has shown to be 85% effective at preventing severe COVID-19 from the B.1.351 variant. 

Are Kids More At Risk for B.1.351?

There is little data currently available for the risk of B.1.351 in children. The virus has been documented in at least one child in the United States, however there is no evidence suggesting this virus causes more severe disease in children and does not suggest increased infection among children.

A Word From Verywell

Experts are worried about the spread of the B.1.351 variant of COVID-19 around the world and in the United States. As this variant is more contagious, it has the opportunity to spread quickly.

Following precautions as outlined by the CDC and getting a vaccine when it is available to you—as long as it safe for you to do so—is important to help decrease the spread of this and other variants of COVID-19.

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.

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Article Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Centers for Disease Control and Prevention. Science brief: emerging SARS-CoV-2 variants. Updated January 28, 2021.

  2. World Health Organization. Weekly epidemiological update on COVID-19 13-April 2021. Updated April 13, 2021.

  3. Washington State Department of Health. First case of B.1.351 variant identified in Washington state as cases of B.1.1.7 increase. Updated February 23, 2021.

  4. Centers for Disease Control and Prevention. COVID-19 tracker. Updated April 19, 2021.

  5. Cleveland Clinic. What does it mean that the coronavirus is mutating? Published January 11, 2021.

  6. Zhou, Daming, et al. Evidence of escape of SARS-CoV-2 variant B. 1.351 from natural and vaccine-induced seraCell (2021).

  7. Centers for DIsease Control and Prevention. How to protect yourself & others. Updated March 8, 2021.

  8. Centers for Disease Control and Prevention. US COVID-19 cases caused by variants. Updated April 10, 2021.

  9. Jassat W, Mudara C, Ozougwu L, et al. Increased mortality among individuals hospitalised with COVID-19 during the second wave in South AfricamedRxiv. Published online March 10, 2021. doi:2021.03.09.21253184