A COVID-19 testing site in Brooklyn earlier this year.

A COVID-19 testing site in Brooklyn earlier this year. Credit: Getty Images / Spencer Platt

Omicron's BA.5 subvariant is now the dominant COVID-19 strain in the United States and accounts for nearly half of infections in the New York region, according to the latest Centers for Disease Control and Prevention data.

While it appears to be less deadly and causes fewer hospitalizations than variants before omicron, this subvariant is especially efficient at infecting vaccinated people, those with natural immunity from previous infections, or both, according to experts.

“What’s been happening with these new variants is, they are becoming more and more and more capable of entering people who are otherwise immune, and the way that it does that is slowly by changing in a way that your body doesn’t recognize it as COVID anymore, or doesn’t react in the same way,” said Sean Clouston, an associate professor and epidemiologist at Stony Brook University who studies population health.

He said that it's likely the spike protein, which coronavirus uses to attach to human cells, has mutated.

What to know

  • BA.5 is efficient at infecting even those who have been vaccinated against COVID-19, previously infected by coronavirus — or both.  
  • Like its relative, the original omicron variant that spread wildly starting last year, BA.5 is apparently less deadly and causes fewer hospitalizations than earlier variants such as delta.
  • BA.5 now accounts for 53.6% of infections nationwide — up from 9.6% a month ago.

According to the CDC data, 46.2% of infections for the week ending July 2 were BA.5 in an agency-designated region that includes New York, New Jersey, Puerto Rico and the Virgin Islands — and 53.6% nationwide. A month ago, BA.5 was 8.5% in the region and 9.6% nationwide.                         

The data comes as the U.S. last month moved closer to updating COVID-19 boosters for the fall: In late June, federal government advisers voted to recommend modified shots that better respond to the latest virus strains.

Although the formula has yet to be decided, it’s anticipated that a tweaked formulation would offer specific protection against omicron and its subvariants, which began to sweep the world starting around Thanksgiving. Omicron and its subvariants are more infectious than previous strains but appear to be less deadly.

In the Mount Sinai health system, the rate of the new subvariant represents between an estimated 25% and 50% of lab tests, according to Dr. Aaron Glatt, the chairman of Mount Sinai South Nassau hospital’s department of medicine.

“The infectiousness of the newer strains is probably more than the older ones, but the likelihood of causing severe illnesses is probably unchanged” from the original omicron, he said.

The omicron wave was itself less deadly and caused fewer hospitalizations than did earlier variants, according to data published by Johns Hopkins.

The BA.5 variant evades natural immunity — which the human immune system develops following a COVID-19 infection — more than the original omicron, Clouston said

"BA.5 is definitely more able to enter a person, no matter what their status is, than the original omicron," he said, citing data found by researchers. 

A letter published June 22 in The New England Journal of Medicine showed "substantial escape" by several variants of omicron, including BA.5, and the research "suggests that the SARS-CoV-2 omicron variant has continued to evolve." 

"These data show that the BA.2.12.1, BA.4, and BA.5 subvariants substantially escape neutralizing antibodies induced by both vaccination and infection," the researchers wrote of the body's beat cops that patrol and attack invading pathogens.  

Still, Glatt said, although vaccination and boosting provide the best protection, even those who are unvaccinated, but have natural immunity from a previous COVID-19 infection, have a reduced chance of hospitalization and death from an additional infection.

The latest subvariants seem to cause more breakthrough infections than even the original omicron.

“It appears to be quite infectious in part because it is better able to infect people who lack one or two boosters and/or who have not been vaccinated recently,” Clouston said in a text message.

"BA.5" comes from an international labeling convention devised by scientists to track virus mutations: "BA" is the technical name for omicron, based on the order in which it was classified, with the number after the period representing the fifth branch on omicron's family tree.

As for how the public, and the government, should respond to the newly predominant variant, Clouston cited the continuing need for boosters, masking in large crowds, and choosing to be outdoors, whenever and wherever possible, such as at summer camp.

“I think people were very excited to basically wipe their hands of COVID, and say, ‘oh, COVID is gone,’ and that’s just not true,” he said. “It’s still here. It’s still hurting people. People are still landing in the hospital. So we want to be aware of that.”

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To get or not get boosted

  • Even as the government considers a new omicron-specific formulation, ideally for the fall, to update the coronavirus vaccine, getting a booster now is recommended — for those who haven't yet gotten one, said Dr. Aaron Glatt of Mount Sinai South Nassau hospital.
  • Other than people in the highest-risk groups, such as those 80 and above, or those with an underlying, severe medical condition, holding off until the next potential booster becomes available is acceptable, Glatt said.

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