The rapid evolution of coronavirus into subvariant alphabet soup presents a daunting challenge to health authorities. They must make extensive policy decisions based on little biological certainty as to which viral variant will prevail this fall or winter.
The Food and Drug Administration announced at the end of June that it would update its coronavirus vaccine for a booster campaign targeting highly infectious Omicron submutants. But the ground is shifting under its feet.
In just eight weeks, the BA.5 subvariant has become the predominant subvariant in the country due to a sharp drop in the number of cases in the United States and now accounts for more than three-quarters of new cases. Probably the most infectious subvariant to date, it promotes positive testing, hospitalization, and admission to intensive care units nationwide.
There is no evidence that BA.5 causes more serious illness, but the latest metrics do break the myth that the virus becomes milder as it evolves.
“None of us have a crystal ball, and we’re trying to use all the last ounces we can do from predictive modeling and the data we have to try to get ahead of the very clever virus. “I will.” Peter Marks, the FDA’s top vaccine regulator, came after the advisory board recommended that authorities prioritize vaccines specific to the Omicron subvariant. “If it’s only nanometers in size, it’s pretty clever. I’m trying to make the best decision here.”
Omicron and its sect have been dominant for about six months, and the upcoming incarnation of the virus is more likely to be linked to the Omicron family than previous versions, said Jerry Weir, FDA’s senior regulator. ..
According to outside experts who do not belong to the FDA’s expert panel, this assumption is the best calculation that can be made at this time.
“Viruses like SARS-CoV-2 are constantly evolving and it is almost certain that new mutants will emerge in the 6-month time frame,” said Jesse Bloom of the Fred Hutchinson Cancer Center in Seattle. increase. “But as long as these mutants are descendants or relatives of BA.2 or BA.4 / BA.5, as the FDA recommends, vaccine boosters based on BA.4 / BA.5 are much more Should be better than the current vaccine, even if it is not an exact match. “
The Centers for Disease Control and Prevention on Tuesday approved a fourth vaccine from Novavax for use in the United States, but the trial was conducted before the advent of Omicron, which could limit its efficacy against mutants. I have.
The Omicron family tree has grown rapidly since Omicron BA.1 was first detected in late November 2021. New federal quote On Tuesday, as of last week, BA.5 was shown to account for about 78% of new cases in the United States.
Emma Hodcroft, a molecular epidemiologist and researcher at the University of Bern, Switzerland, said the evolutionary pattern of Omicron differs from previous varieties. “The kids in Delta weren’t dominant, but the kids in Omicron are pushing their siblings if you do,” she said. “This suggests that Omicron is at its peak and there are small changes.”
More Omicron children may be on the way, but she and other scientists emphasized that it does not prevent another variant from appearing.
Nathan Gourbo, an epidemiologist at the Yale School of Public Health, said: Last fall, he correctly predicted the emergence of an antigenic escape subvariant, but his expectation that it would come from a delta variant was wrong.
“Obviously, we are now seeing new variants (BA.2, BA.4, and BA.5) emerging from within Omicron, which may continue,” he said. Said. “But we should think that it is unimaginable and that it will continue.”
Last year, Sarah Cobey, an evolutionary biologist at the University of Chicago, was almost convinced that the next variant would derive from Delta. “Still, I think the next variant is very likely to be derived from Omicron,” she said last week, adding that the degree of antigenic escape could be greater or more contagious. rice field. “The following variants may have already appeared, but will avoid surveillance for some time,” she said.
The sinister Omicron cousin, BA.2.75, is already found in parts of the world.
Tweaking the booster shot formula is more important, according to Christian Andersen, a virologist at the Scripps Research Institute in La Jolla, California. A particular variant, he said. He says that early variants evolved from early lineages rather than from previous variants, making them difficult to predict, unlike Omicrons.
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“For decades we’ve been trying to better guess the next influenza variant,” said Dr. Hodcroft. “And it turned out to be very complicated.”
Many variables mean that she and other professionals cannot make a declaration with complete confidence. She states: “It’s very difficult to put all of this in a machine and grind it.”
