New Omicron Strains Hint That Big Covid-19 Waves Are on the Way

SARS-CoV-2 has a tough hurdle nearly three years into the pandemic: discovering new ways around the immunity people have built up through vaccines and innumerable infections. Worrying about new data indicates that it is up to the task. Several novels and highly immune-evasive strains of the virus have gained the attention of scientists in recent weeks; one or more of these may well generate large, fresh COVID-19 outbreaks this fall and winter.

“With sure, something is on the way.” “More than likely, numerous things are on the way,” says Cornelius Roemer, a viral evolution researcher at the University of Basel. The main concern is whether they will also result in a high number of hospitalizations and deaths.

“It’s not surprising that we’re seeing changes that help the virus evade immune responses yet again,” says University of Bern molecular epidemiologist Emma Holcroft, who notes that SARS-CoV-2 faces “the same challenge that things like the common cold and influenza face every year—how to make a comeback.”

The strains that appear to be driving the recent return are all subvariants of Omicron, which swept the world last year. Several were generated from BA.2, a strain that replaced the original BA.1 strain of Omicron but was later outcompeted in most regions by BA.5, which has recently dominated.

One of them, BA.2.75.2, appears to be rapidly expanding throughout India, Singapore, and portions of Europe. Other novels immune-evading strains have emerged from BA.5, including BQ.1.1, which has been detected in a number of places throughout the world.

Despite their disparate beginnings, several of the new strains have acquired a similar set of mutations to enable them to scale the immune wall—a fascinating example of convergent evolution. According to evolutionary biologist Jesse Bloom of the Fred Hutchinson Cancer Research Center, they all have alterations at half a dozen crucial sites in the viral genome that determine how efficiently neutralizing antibodies from vaccination or past infection attach to the virus.

Researchers produce replicas of the viruses’ spike proteins and expose them to monoclonal antibodies or sera from people to see how well the antibodies can prevent the variants from infecting cells. Using similar testing, researchers in China and Sweden discovered that the spike protein from BA.2.75.2 can successfully dodge nearly all monoclonal antibodies used to treat COVID-19, implying that conventional treatments may become obsolete.

New Omicron Strains Hint That Big Covid-19 Waves Are on the Way

Both groups discovered that BA.2.75.2 appears to be highly good at bypassing human immunity. Immunologist Ben Murrell of the Karolinska Institute and his colleagues reported in a preprint published on September 19 that serum samples from 18 blood donors in Stockholm—where vaccination rates are high and prior infections are common—were less than one-sixth as effective at neutralizing BA.2.75.2 as BA.5. “This is the most resistant version we’ve ever assessed,” says Daniel Sheward, a virologist at Karolinska Institutet.

Yunlong Richard Cao, an immunologist at Peking University, and his colleagues discovered similar results for BA.2.75.2 after testing blood samples from 40 people who had been vaccinated with three doses of CoronaVac, an inactivated virus vaccine, and 100 more who had been vaccinated but then developed breakthrough infections with BA.1, BA.2, or BA.5. The researchers discovered that BQ.1.1 had a similar remarkable capacity to avoid antibodies.

Cao and his colleagues also report in their preprint, which was updated on September 23, that the new variants do not appear to have lost any ability to bind tightly to the receptor on human cells that the virus uses to infect them, implying that the variants’ infectiousness has likely not decreased.

They also found evidence that infections with the variations cause an increase in the wrong types of antibodies—those that bind strongly to the virus but do not impair its capacity to infect cells. Cao believes that all of this could herald a tremendous new wave. “The extent of immune evasion has never been observed before,” he says, adding that the virus is still rapidly changing. “It’s terrible.”

Sheward and Murrell both think that we should expect a spike in infections in the coming months, similar to what happened last winter when Omicron entered the picture. They are, however, less pessimistic than Cao, noting that many more patients have recovered from an infection or have received additional vaccination doses, including Omicron-specific boosters, which began rolling out this month.

Sheward believes that they will increase overall antibody levels and likely widen the antibody repertoire: “I don’t think we’re exactly back to square one.”

“The decision to include BA.5 in the vaccination booster appears to be a wise one,” Bloom adds. “The boosters will always be a step behind, but the good news is that the BA.5 booster will be one or two steps behind the virus’s evolution, rather than five.”

The severity of the coronavirus’s resurgence will become obvious as more people become sick with the new variants. The next wave may potentially reveal more information about what factors cause or avoid severe sickness, according to Murrell: “I think we’re going to learn a lot this winter.”

Comments are closed.