China News Service, January 4th. Recently, the spread of the subtype XBB.1.5 of the Omicron mutant strain in the United States and other countries and regions has aroused concern and concern from the outside world.

Will this strain trigger a new wave of outbreaks and lead to more severe disease?

Will the vaccine still work for it?

How should people protect themselves?

Data map: A new crown virus testing station on 14th Street in Manhattan, New York, USA, tests residents.

Photo by China News Agency reporter Liao Pan

Will the XBB.1.5 strain "sweep" the United States?

  XBB is a recombinant strain of two mutant strains BJ.1 and BM.1.1.1 derived from the new coronavirus Omicron BA.2.

XBB.1.5 is a sub-branch derived from XBB.

  The British "Independent" quoted statistics from the Global Influenza Sharing Database (GISAID), showing that XBB.1.5 has been found in at least 74 countries and regions, including the United States, the United Kingdom, India, and Pakistan.

Among them, the strain was detected in 43 states in the United States.

  According to CNN, in the fall of 2022, XBB set off a wave of epidemics in Singapore.

Now, XBB.1.5 may be driving a new wave of epidemics in the United States.

  The U.S. Centers for Disease Control and Prevention (CDC) expects that XBB.1.5 will account for a substantial increase in the weekly share of new coronavirus infections compared to other strains, with the share of new infections rising from about 4% to 41% in December 2022. %.

The CDC also estimates that in the northeast of the country, XBB.1.5 is responsible for about 75% of new cases.

  "We haven't seen a variant spreading at this rate in months," said Pavitra Roychoudhury, director of coronavirus sequencing at the Virology Laboratory at the University of Washington School of Medicine.

  Trevor Bedford, a professor of computational biology at the Fred Hutchinson Cancer Research Center in Seattle, also said, "Expect it to drive transmission growth in the coming weeks."

  He noted that this increase may not be reflected in case numbers as more people choose to be tested at home.

"I would therefore like to see hospitalizations in vulnerable age groups, such as the elderly, as a more appropriate wave indicator."

Data map: The picture shows people eating outdoors on a food street in London.

Photo by Zhang Mengqi issued by China News Agency

Two major features may boost the spread of XBB.1.5

  CNN pointed out that the reason why XBB.1.5 may promote the spread of new epidemics is related to its two characteristics.

  One is its extremely "cunning" immune escape ability.

  Dayi Ho, a professor of microbiology and immunology at Columbia University, recently tested viruses in his lab that were engineered to have spikes of XBB and XBB.1, as well as BQ.1 and BQ 1.1, against different types of subjects' blood Antibodies in, including groups infected with the virus, groups vaccinated with the original strain and the bivalent vaccine, and groups infected with the virus and vaccinated.

His team also tested 23 monoclonal antibody therapies against these new sublines.

  The study found that XBB.1 was "the most devious" of them all.

It was 63 times less likely to be neutralized by antibodies in the blood of infected and vaccinated individuals than BA.2 and 49 times less likely than BA.4 and BA.5.

Furthermore, in terms of immune evasion, these variants have been "far away" from the antibodies humans make against them.

  Ho called the level of immune escape "worrying" and said it could further compromise the efficacy of the COVID-19 vaccine.

XBB.1.5 is identical to XBB.1 in terms of antibody escape, meaning it has the potential to escape protection from vaccination and past infection.

It also resisted all current antibody treatments.

  In addition to the high immune escape ability, another "skill" of XBB.1.5 that may help spread is that the strain has a key mutation at position 486, which allows it to bind more tightly to ACE2.

ACE2 acts as the "gate" that viruses use to enter human cells.

  "This mutation clearly allows XBB.1.5 to spread better," says Jesse Bloom, a computational virologist at the Fred Hutchinson Cancer Center.

  Still, experts say it's hard to know to what extent XBB.1.5's growth can be attributed to the nature of the virus or the timing of its spread.

During the holidays, for example, people are likely to socialize and travel, and that gives any infection — whether it’s the flu, COVID-19 or RSV — more room to spread.

Data map: Passengers arrive at the arrival area of ​​international flights at San Francisco International Airport, California, USA.

Photo by China News Agency reporter Liu Guanguan

Will XBB.1.5 cause more severe disease?

  It is worth noting that most experts expect that XBB.1.5 will likely lead to more infections, but they do not think that these infections will necessarily be more serious.

  Michael Osterholm, who directs the Center for Infectious Disease Research and Policy at the University of Minnesota, said the updated booster should provide some protection, even against strains such as XBB.1.5, which are highly immune-evading.

  "They still provide a level of immunity that may not prevent you from getting infected, but could have a significant impact on whether you get seriously ill and die," he said. For those who were not vaccinated, their risk of death was three times lower than those who were not vaccinated."

  CNN pointed out that rapid testing, wearing masks, ventilating and filtering indoor air, etc. will also continue to play a role, so even if the virus continues to evolve, people still have good ways to protect themselves from infection.

  "It doesn't seem to be causing any more severe disease, so I think the epidemic is very different today than it was a year ago," Osterholm said.