XBB.1.5 COVID-19 subvariant: 4 Fast Facts

A new COVID-19 subvariant of omicron, XBB.1.5, is distinctive because of how fast it spreads. It’s quickly outcompeting other strains of the virus in regions where it has been spreading, and is now the dominant strain in the Northeast U.S., where XBB.1.5 was first discovered in October 2022.

Some people online have taken to calling the new subvariant “kraken” following its quick explosion in the Northeast United States.

VERIFY has put together four fast facts with what you should know about XBB.1.5.

THE SOURCES

• News post by scientific journal Nature 
• Johns Hopkins University Bloomberg School of Public Health
• World Health Organization (WHO)
• Centers for Disease Control and Prevention (CDC)
• The Mayo Clinic
• College of Physicians of Philadelphia
• The American Medical Association
• Gavi, the global vaccine alliance
• William Schaffner, M.D., a professor of infectious diseases at Vanderbilt University

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WHAT WE KNOW

1. What is XBB.1.5?

XBB.1.5 is a subvariant of omicron, which is itself a variant of SARS-CoV-2, the virus that causes COVID-19. 

So what makes XBB.1.5 different from the original SARS-CoV-2? XBB.1.5 is the result of the virus undergoing many mutations over the past three years, most of which change how well the virus spreads, and the severity of the disease it causes.

What makes XBB.1.5 unique among the variants and subvariants of the original virus is that it has more mutations to evade immunity than any of its predecessors, Johns Hopkins University says.

It’s extremely contagious, says William Schaffner, M.D., a professor of infectious diseases at Vanderbilt University, but it isn’t producing more severe disease than previous strains of the virus.

2. Where is XBB.1.5 spreading?

As of Jan. 11, 2023, XBB.1.5 is primarily in the Northeastern United States, particularly in New York, where the subvariant was first detected. 

According to the Centers for Disease Control and Prevention (CDC), XBB.1.5 is believed to make up more than 70% of cases in the Northeastern U.S., but only about 28% of cases across all of the United States. That makes it the second-most prevalent strain in the country. BQ.1.1 is currently the only strain more pervasive, after just two months since it first began spreading.

But experts say XBB.1.5 may become the dominant COVID-19 strain across all of the U.S., and may even spread rapidly across the globe.

3. How infectious is XBB.1.5?

Experts believe XBB.1.5 is extremely infectious, both because of its transmissibility and its ability to evade immunity from both previous infections and vaccinations.

The WHO says XBB.1.5 poses a higher risk of reinfection for people who have been sick with previous strains of omicron, compared to other currently circulating subvariants of omicron such as BA.5. And although lab studies suggest that vaccination offers significant protection against serious disease, it might not offer as much protection against mild infection from XBB.1.5, Johns Hopkins University says.

An article in the scientific journal Nature explains that this ability to dodge immunity comes from a mutation inherited from the first version of XBB. That version of the strain then mutated again to more easily attach to cells in the nose and throat, creating XBB.1.5.

The increased ability to enter the respiratory system means XBB.1.5 spreads from person to person more effectively than its ancestors.

4. What are XBB.1.5 infections like?

So far, XBB.1.5 infections are similar to those caused by other omicron subvariants, Andrea Garcia, J.D., wrote in an American Medical Association article. That means its disease is typically milder than some other variants such as Delta.

“So far the symptoms of XBB.1.5 seem to be more cold-like than flu-like, especially in people who have been vaccinated or have had COVID-19 before, but it is too soon to say this definitively,” Gavi, the global vaccine alliance, has reported.

These symptoms typically include cough, runny nose, sore throat, fever and muscle ache, according to the Mayo Clinic.

“Now, there are two very fortunate things about XBB.1.5,” Schaffner said. “And the first is that it is not producing more severe disease. Excellent. And also, our currently available vaccines continue to provide substantial protection against severe disease — disease bad enough to require hospitalization.”