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Coronavirus Variants: What We Know So Far

Scientists are scrambling to learn more about new strains that are more contagious

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En español | Public health officials have identified new strains of the coronavirus that are more contagious, worrying experts who say they could lead to a surge in COVID-19 cases just as vaccinations are getting underway. 

The first variant, known as B.1.1.7., was discovered in the United Kingdom but is now circulating in more than 30 countries and at least 23 U.S. states. It may become the dominant strain in the U.S. by March, the Centers for Disease Control and Prevention (CDC) said.

Preliminary data indicate that the U.K. strain could lead to more deaths, but experts caution that more research is needed. Studies so far indicate the current COVID-19 vaccines will be effective against it.

Another concerning variant was first identified in South Africa. Known as B.1.351, it was discovered in the U.S. on Jan. 28, when health officials announced it had infected two people in South Carolina. The patients had no history of travel or of contact with each other, which suggests it is already spreading in the community.

The South African variant has worried scientists because it contains a mutation that could allow the virus to elude some of the antibodies produced through vaccines.

Preliminary data released Jan. 28 indicate the Pfizer-BioNTech vaccine may lose only a small amount of effectiveness against it.

Vaccine maker Moderna, meanwhile, has already announced that it is working to modify its vaccine and to create a booster shot to better protect against it.

A third variant was discovered in Brazil but has not yet been found in the U.S. 

The variants are up to 70 percent more transmissible than the original coronavirus.

“Because the variants spread more rapidly, they could lead to more cases and put even more strain on our heavily burdened health care systems,” said Henry Walke, M.D., incident manager for the CDC’s COVID-19 response team.

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How did these new COVID-19 strains develop?

Because viruses multiply rapidly, new mutations are always occurring, said William Schaffner, M.D., an infectious diseases specialist at Vanderbilt University Medical Center in Nashville, and medical director of the National Foundation for Infectious Diseases (NFID). 

Most of these tiny genetic changes have no effect on the behavior of the virus. 

The new variants discovered in the U.K., South Africa and Brazil stood out because they spread more easily, Schaffner said, so they can rapidly replace other versions of the virus and become dominant. 

Are the new strains more dangerous?

A U.K. report released Jan. 22 states there is "a realistic possibility" that the U.K. variant is associated with a higher death rate in infected patients, although more data is needed to know for sure.

The CDC has said it is reviewing the U.K. report.  

Because variants are more contagious, they may also be able to infect more people more quickly, potentially increasing overall hospitalization and death rates.

Scientists estimate the U.K. variant is 40 to 70 percent more transmissible than the traditional COVID-19 virus. Its spread has led to a rapid spike in cases in England; figures released in January showed that 1 in 50 people there had recently been infected with the virus.

Will the COVID-19 vaccine work against the new strains?

Early studies indicate both the Moderna and Pfizer-BioNtech vaccines will work well against the U.K. mutation.

The South African variant has been more of a question mark, Schaffner said, because it contains a mutation that may allow the virus to elude some of the antibodies produced through vaccines.

Moderna has already announced it is working on an updated version of its vaccine that will be tailored to that strain. It is also developing a booster shot that could be given to people who have already received the original vaccine.

Pfizer-BioNTech released early data on Jan. 28 that indicates its vaccine will be mostly protective against the strain. The company said it could modify its vaccine quickly if needed to match any new variants that arise.   

What precautions should you take? 

The guidance about how to protect yourself from COVID-19 hasn’t changed: Wear a mask, wash your hands, practice social distancing, avoid crowds and stay home if you can.

“These strains reinforce the importance of all of the standard interventions we’ve been talking about, because they work,” Schaffner said. “And when it comes your turn to get the vaccine, by all means get the vaccine.”

Editor's note: This story, orginally published on January 8, 2021 has been updated with new information.

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