A highly mutated strain of the coronavirus is less of a threat than previously feared, according to new research led by Boston scientists, allaying concerns that it will trigger a new global surge in infections.
The BA.2.86 subvariant raised alarms worldwide in recent weeks because it carries more than 30 mutations in its spike protein compared with its parent virus, BA.2, and the most recent highly circulating strain, XBB.1.5
Those alterations were similar to what scientists saw in the Omicron variant, which caused the pandemic’s largest wave of hospitalizations and deaths in late 2021. The virus uses the spike protein to enter human cells.
The new strain has been detected in small numbers in 10 countries, and data suggests it has been spreading quietly.
“The combination of the large number of mutations and that it seemed to have emerged in many countries around the world at the same time raised the specter that it could be a variant that causes substantial concern,” said Dr. Dan Barouch, a professor of medicine at Harvard Medical School and the director of the Center for Virology and Vaccine Research at Beth Israel Deaconess Medical Center. “That’s why many research groups throughout the world have been trying to generate as much info as quickly as they could about it.”
In a preprint paper, a team led by Barouch reported that people’s immune systems were able to fight off BA.2.86 as well as, if not better than, other circulating variants.
The Beth Israel study also found that the immune response is robust against all variants — including BA.2.86 — after exposure to an XBB infection, which would likely include anyone who contracted COVID-19 since December 2022. That’s particularly good news for the upcoming booster, which is set to be released mid-September and was formulated based on XBB.1.5.
Though booster shots may help protect against current strains of the virus, people should remain on guard, Barouch said. There is variation in the degree to which different strains can evade the immune system, and the study found that two other currently circulating strains — EG.5 and FL.1.5.1 — are more immune-evasive than earlier strains. Those variants are likely the reason for the country’s modest uptick in infections.
“I do think the battle is far from won,” Barouch said. “We will continue to see new variants, some of which will become more problematic than others. I do think we need to remain vigilant in evaluating further possible evolution of BA.2.86. It could also recombine with some of the current variants to produce a variant that is potentially more problematic than the ones we have today.”
The Beth Israel study looked at samples from 66 individuals — some who had been vaccinated with a bivalent booster last fall, and others who did not receive the booster. Most of the individuals had also had at least one documented COVID infection.
The robust immune response to BA.2.86, though surprising, makes sense due to the lineage of the virus, Barouch said. The newer variant is more immune-evasive than the parent virus it evolved from, generating a tenfold lower antibody response than BA.2. However BA.2 is an older, less immune-resistant strain.
The Beth Israel data are consistent with recent research out of China, Sweden, and Columbia University, and for now have been met with a big sigh of relief from those in the scientific community.
Dr. Ashish Jha, dean of the School of Public Health at Brown University, who previously served as the White House COVID-19 response coordinator, said that when he initially saw BA.2.86, he was worried the upcoming booster would offer very little protection against it. But the studies have given him some assurance that the new variant does not pose as significant of a threat.
While this most recent strain isn’t as concerning as once thought, the possibility still exists that another large evolutionary change could lie ahead.
How well a virus evades the immune system is also only one part of the equation. Bill Hanage, an associate professor of epidemiology and associate director of the Center for Communicable Disease Dynamics at the Harvard T. H. Chan School of Public Health, said scientists also need to be mindful of how quickly the virus copies itself, and which part of the body it replicates in, to better gauge its transmissibility. For example, viruses that replicate toward the front of the nose might be easier to transmit than those that replicate deeper in the body.
While the virus isn’t showing large spikes in transmission today, it may still prove to be the dominant variant in a couple of months.
“The proof of the pudding will be in the epidemiology,” he said. “Thus far, it doesn’t look explosive. It’s too early to make bigger claims or [predict] what will happen in the fall and winter.”
Jha said that surveillance has to continue, particularly of waste water, to ensure we understand how the virus is continuing to evolve. Half of the country lives in a location where waste water surveillance is taking place, and only one-third of the world is conducting such surveillance.
As the public awaits the new boosters, deciding whether or not to take more intensive precautions is a personal choice, he said.
According to Jha, we will likely see two to three waves of COVID each year. During larger or more intense waves, masking makes sense. But, so far this summer, infections are at levels that are less than half of last summer’s peak. The most important thing most people can do is stay up to date on vaccinations and boosters and get treated when they have an infection. The degree to which people use distancing, testing, and masking depends on people’s individual risk profiles, particularly when the region isn’t in a massive wave, he said.
As the country takes a longer-term approach to the pandemic, facts and science should ultimately drive how the country responds.
“We have to be humble around our initial expectations,” Jha said. “Concern has to be followed up with data and data has to drive policy. That’s where we’re going to be for a while.”