‘None of us has a crystal ball’: Scientists try to keep up with faster coronavirus evolution.

The rapid evolution of the coronavirus in an alphabet soup of subvariants presents a formidable challenge to health officials: They must make far-reaching policy decisions based on little biological certainty of which viral variants will dominate this fall or winter.

The Food and Drug Administration said in late June that it would update coronavirus vaccines for a booster campaign in the fall targeting the highly infectious Omicron subvariants. But the ground is slipping under his feet.

In just eight weeks, the BA.5 subvariant has gone from a blip in the US case to the dominant subvariant in the country, now making up more than three-quarters of new cases. Perhaps the most transmissible subtype by far, it continues to lead to positive tests, hospitalizations and admissions to intensive care nationwide,

There is no evidence that BA.5 causes more severe disease, but the latest metrics certainly bust the myth that the virus will get milder as it develops.

“None of us have a crystal ball, and we’re trying to use every last ounce of that data from predictive modeling and that we have to try to overtake a virus that’s so smart.” ,” Doctor. An advisory committee recommended that the agency prioritize vaccines specific to the Omicron subvariant, followed by Peter Marks, a top vaccine regulator at the FDA. “For something that’s only a nanometer in size, that’s pretty clever. We’re trying to make our best judgment here.”

Jerry Weir, a senior FDA regulator, said Omicron and its offshoots have dominated for about six months now, and whichever incarnation of the virus it comes with, it is more likely to come from the Omicron family than earlier versions.

This assumption is the best calculation that can be made at this time, according to outside experts not in the FDA expert panel.

“Viruses like SARS-CoV-2 are always evolving, and it’s almost certain that new mutants will emerge in any six-month time frame,” said Jesse Bloom of the Fred Hutchinson Cancer Center in Seattle. “But as long as these mutants are descendants or close relatives of BA.2 or BA.4/BA.5, a vaccine booster based on BA.4/BA.5, as recommended by the FDA, should be much better Matches them in comparison to existing vaccines, even if it is not a perfect match.”

The Centers for Disease Control and Prevention on Tuesday approved a fourth vaccine from Novavax for use in the United States, but its trials were conducted before Omicron’s emergence and may have limited its effectiveness against the variant.

The Omicron family tree has been growing rapidly since Omicron BA.1 was first detected in late November 2021. New federal estimates on Tuesday showed that BA.5 made up about 78 percent of new cases in the United States as of last week.

Emma Hodcroft, a molecular epidemiologist and researcher at the University of Bern in Switzerland, said the growth pattern of the omicron diverged from that of earlier forms. “Delta’s kids weren’t prime, but Omicron’s kids are taking their siblings out, if you will,” she said. “This is indicating that Omicron is peaking and there will be small changes.”

Although more Omicron babies may be on the way, he and other scientists emphasize that nothing will prevent another kind from appearing.

“Many times we have predicted how we think SARS-CoV-2 will develop and then vehemently wrong,” said Nathan Grubaugh, an epidemiologist at the Yale School of Public Health. Last fall, he correctly predicted that an immune-suppressing subvariant would emerge, but his expectation that it would come from the delta variant was wrong.

“Obviously, we are seeing new variants emerge from within Omicron right now – BA.2, BA.4, and BA.5 – and that could continue to happen,” he said. “But we should not become the unthinkable and think that this will continue.”

Last year, Sarah Kobe, an evolutionary biologist at the University of Chicago, was almost certain that the next version would descend from Delta. “I still think it is very likely that the next version will descend from Omicron,” she said last week, adding that it may have immune evasion or increased transmittance. “It is likely that the next version has already come out, but will escape surveillance for some time,” she said.

An unlucky Omicron cousin, BA.2.75, is already being observed in some parts of the world.

That makes the formula for booster shots all the more important, according to Kristian Andersen, a virologist at the Scripps Research Institute in La Jolla, California. The benefits of such a move have more to do with boosting immunity than with increased protection. specific version, he said. Unlike Omicron, he said, early variants did not evolve from previous variants, but from earlier lineages, making predictions difficult.

Forecasting, however, is the stock of every expert in the business.

“We’ve been trying to better predict the next flu version for decades,” Dr. Hodcroft said. “And it turns out it’s very complicated.”

Many variables mean that he and other experts cannot declare with complete confidence. She said: “It’s very hard to put all these in one machine and crunch it.”