What We Know About California COVID Variant B.1.427/B.1.429

A new coronavirus variant that was first identified in California is now taking hold in some parts of the state—but what do we currently know about it?

The variant actually comes in two forms, known as B.1.427 and B.1.429, both of which carry a similar, albeit slightly differing, set of genetic mutations—including three that affect the spike protein of the SARS-CoV-2 virus.

The spike protein enables the virus to bind on to and enter human cells. One of the mutation that B.1.427 and B.1.429 carry—dubbed L452R—is thought to increase the infectivity of the virus.

Scientists think B.1.427/B.1.429 first emerged in late spring or summer of 2020 before it was first detected by researchers from the University of California, San Francisco, in December. It has now been found in at least 45 U.S. states and several countries around the world, although California is the only place it has taken hold significantly.

Researchers from UCSF have documented the spread of the variant in the state in a paper that has yet to be peer-reviewed or posted online, but was reported on by outlets such as the New York Times and Science magazine.

For their study, the researchers examined 2,172 SARS-CoV-2 virus samples collected from patients in 44 California counties between September 1, 2020, and January 29, 2021, according to Science. The scientists found that the prevalence of the variant among the samples increased drastically from zero to more than 50 percent over this time period.

The UCSF researchers also say that cases caused by the variant are now doubling every 18 days, the Times reported.

The scientists say their data indicates that B.1.427/B.1.429 is more transmissible than the original virus while also being associated with more severe disease—although more research needs to be conducted before either of these conclusions can be confirmed.

"This variant is concerning because our data shows that it is more contagious, more likely to be associated with severe illness, and at least partially resistant to neutralizing antibodies," senior author of the study Charles Chiu, an infectious diseases physician at UCSF, told Science.

In fact, the authors wrote in the study that B.1.427/B.1.429 "should likely be designated a variant of concern warranting urgent follow-up investigation," based on the available evidence.

Evidence to suggest that the variant is more contagious comes, in part, from the finding that people infected with it had about twice as much of the virus in their nose compared to others, which could make them more infectious, according to Science.

Robert Schooley, an infectious disease expert at UC San Diego, who was not involved in the research, told Science: "The biology of having a higher level of virus... would certainly fit the thesis that people would not do as well."

Other epidemiological data from nursing home and household settings collected by UCSF researchers supports the hypothesis of higher transmissibility, although B.1.427/B.1.429 may not be as infectious as other variants, such as B.1.1.7, which was first identified in the U.K. and has spread widely across the United States.

"I'm increasingly convinced that this one is transmitting more than others locally," William Hanage, an epidemiologist at the Harvard T.H. Chan School of Public Health, who was not involved in the research, told the Times. "But there's not evidence to suggest that it's in the same ballpark as B.1.1.7."

Data from the study regarding COVID-19 patients found an association between B.1.427/B.1.429 and more severe disease. Among more than 300 people with COVID-19 who were cared for at UCSF clinics or its medical center, those infected with the variant were 4.8 times more likely to be admitted to the ICU and 11 times more likely to die than patients with other variants, the study found, according to Science.

But the authors admit it is not possible to conclude from these figures that the variant actually causes more severe disease.

"If I were a reviewer, I would want to see more data from more infected people to substantiate this very provocative claim," David O'Connor, a virus expert from the University of Wisconsin, Madison, who was also not involved in the research, told Science.

Hanage told Science that, unlike the UCSF scientists, he does not believe B.1.427 and B.1.429 should be categorized as variants of concern based on their study alone.

"The work is definitely worth reporting, but I don't buy that on its own this is sufficient to categorize these as variants of concern," Hanage told Science.

He also told the Times that B.1.427/B.1.429 is "not as big a deal as the others." B.1.1.7, for example, has tended to explode rapidly in new countries where it appears, whereas this does not appear to be the case with B.1.427/B.1.429.

Chiu told the Times that it's possible B.1.427/B.1.429 could surpass B.1.1.7 in California, but only time would tell.

Health worker checks temperature of motorist
A motorist wearing a face mask gets his temperature checked by a health care worker at the Southside Church of Christ in Los Angeles, California, on January 18, 2021. RINGO CHIU/AFP via Getty Images