What Are the B.1.427 and B.1.429 Variants?

What to know about these COVID-19 mutations, also known as the epsilon variants

Two of the recent COVID-19 variants—B.1.427 and B.1.429—are often found together. These variants were discovered in California in February 2021 and were classified as “variants of concern” by the World Health Organization in March 2021.

Coronavirus closeup

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Where B.1.427 and B.1.429 Have Spread

The B.1.427 and B.1.429 variants, also known as the Epsilon variants, have now spread from the United States to at least five countries worldwide.

Spread in the United States

The B.1.427 and B.1.429 variants were initially found in California in February 2021, but are no longer the dominant strains in the state.

As of June 8, 2021, the B.1.427 and B1.429 variants were responsible for about .5% of new cases in the U.S. overall and were expected to continue declining. Although, they still accounted for 5% of cases in California and more than 9% of cases in Washington and Oregon.

They have been found in at least 28 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.

Are B.1.427 and B.1.429 More Contagious?

The B.1.427 and B.1.429 variants are thought to be more contagious than the original COVID-19 virus based on data from the United States. Some studies have suggested a 20% increased transmission rate with the B.1.427 and B.1.429 variants.

The infectiousness of a virus is measured by a reproduction number—called R0—which measures the number of people an infected person will give the virus to. For example, if the R0 is 1, an infected person is likely to give it to one other person; an R0 of 5 means an infected person is going to transmit it to five other people. We do not yet know the R0 for the B.1.427 and B.1.429 variants.

Preventing Transmission

Precautions to prevent the transmission of the B.1.427/B.1.429 variants are the same as for the original COVID-19 virus and should continue to be followed. Precautions if you're unvaccinated include:

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

If you are fully vaccinated, the CDC has released new guidelines that say you can go without a mask and physical distancing in places where it isn't required by federal, state, or local regulations.

Regular hand washing is still recommended.

Risk of Reinfection

There aren't any currently reported data regarding the risk of reinfection of COVID-19 due to the B.1.427 and B.1.429 variants.

Is B.1.427/B.1.429 More Severe?

Data on the severity of COVID-19 infection from the B.1.427 and B.1.429 variants is limited. At this time, there is no evidence to suggest that the B.1.427 and B.1.429 variants cause more severe disease.

Recent studies did uncover that specific monoclonal antibody treatments may be less effective for treating cases of COVID-19 caused by the B.1.427 and B.1.429 variants.

Will Vaccines Work Against B.1.427/B.1.429?

The World Health Organization (WHO) has reported that the B.1.427 and B.1.429 variants may cause a mild decrease in the effectiveness of vaccines. Studies are still ongoing, and more information will continue to be released.

Are Kids More At Risk for B.1.427/B.1.429?

There is little data currently available about the risk of the B.1.427 and B.1.429 variants in children. However, there is no evidence suggesting these variants cause more severe disease in children and does not suggest increased infection among children. 

A Word From Verywell

Even though the B.1.427 and B.1.429 variants of COVID-19 are declining in the United States, experts are still concerned about their spread in the U.S. and the world. As these variants are more contagious, they have the opportunity to spread quickly.

Following precautions as outlined by the CDC and getting a vaccine when it is available to you are important to help decrease the spread of these 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
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  1. Centers for Disease Control and Prevention. About variants of the virus that causes COVID-19. Updated June 15, 2021.

  2. Centers for Disease Control and Prevention. COVID data tracker: variant proportions. Updated June 15, 2021.

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

  4. Centers for Disease Control and Prevention. SARS-CoV-2 variant classifications and definitions. Updated June 15, 2021.

  5. Centers for Disease Control and Prevention. How to protect yourself & others. Updated June 11, 2021.

  6. Centers for Disease Control and Prevention. When you've been fully vaccinated. Updated June 17, 2021.

  7. Virginia Department of Health. First cases of B.1.427 and B.1.429 COVID-19 variants reported in Virginia. Published March 25, 2021.