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

What to know about these COVID-19 mutations

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

Radoslav Zilinsky / Getty Images

Where B.1.427 and B.1.429 Have Spread

The B.1.427 and B.1.429 variants have now spread from the United States to at least 27 countries worldwide.

Spread in the United States

The B.1.427 and B.1.429 variants were initially found in California in February 2021, and are now the dominant strain in the state. The B.1.427 and B1.429 variants are responsible for 2.9% of new COVID-19 cases in the United States. They have been found in 26 states so far.

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. 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 Centers for Disease Control and Prevention (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

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

Experts are worried about the spread of the B.1.427 and B.1.429 variants of COVID-19 around the world and in the United States. 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.

Was this page helpful?
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. About variants of the virus that causes COVID-19. Updated April 2, 2021.

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

  3. Centers for Disease Control and Prevention. COVID data tracer: variant proportions. Updated March 27, 2021.

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

  5. Centers for Disease Control and Prevention. SARS-CoV-2 variant classifications and definitions. Updated March 24, 2021.

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

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

  8. Virginia Department of Health. First cases of B.1.427 and B.1.429 COVID-19 variants reported in Virginia.