The new variants will keep covid-19 in circulation throughout the boreal summer

The new subvariants of the coronavirus: XD, XE and XF 2:21

(CNN) --

As the United States grapples with the latest wave of COVID-19, new research suggests looming variants may keep case levels elevated.

The next infections will likely come from new omicron subvariants BA.4 and BA.5, two closely related viruses that were first described in South Africa and arrived in the United States in late March, according to the genetic sequence exchange site. GISAID.

These subvariants are gaining ground on the BA.2 subvariant, especially in the central zone of the country.

Recent research suggests that they evade the immunity created by vaccinations and previous infections.

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  The key seems to be in the omicron variant

According to the most recent updates from the US Centers for Disease Control and Prevention (CDC) and the genomics company Helix, it is estimated that the BA.4 and BA.5 variants accounted for jointly between 6% and 7% of new infections in the US at the end of May.

"This is a serious threat," Dr. David Ho, a professor of microbiology and immunology at Columbia University in New York, wrote in an email.

"Just a month ago, it was 0.02%."

The BA.4 subvariant has been detected in at least 30 countries, and BA.5 has been sampled in 32 countries, according to the Scripps Research Institute's Outbreak.info website.

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Ho and his co-authors recently analyzed antibodies from the blood of vaccinated and boosted people, as well as antibodies from people who had recovered from Covid-19 infections, against laboratory-created BA.4 and BA.5 virus specimens.

In each case, they found decreased potency against BA.4 and BA.5.

They found that the BA.4 and BA.5 viruses are more than four times more likely to evade antibodies in people who have been vaccinated and have received boosters compared to the BA.2 subvariant.

More post-vaccination infections

All this means that the BA.4 and BA.5 subvariants are more likely to cause post-vaccination infections, even in people who have been infected with covid-19 before.

Without up-to-date vaccinations and boosters, Ho expects many Americans to get sick in the coming weeks or months.

"I think we're going to see a lot of infections, but not necessarily more serious illnesses or deaths," he said.

Ho's research is published as a preprint, meaning it has not been peer-reviewed or published in a medical journal.

South Africa, which is ahead of the US in its BA.4/BA.5 cycle, has seen an increase in infections but not a corresponding increase in deaths, said Shishi Luo, associate director for bioinformatics and infectious diseases at Helix.

"So I think if we extrapolate from South Africa, what we will see in the US is that BA.4 and BA.5 will increase, because they have some competitive advantages compared to existing strains, but fingers crossed, it's not going to lead to more serious outcomes," Luo said.

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One of the questions variant finders have been asking is whether BA.4 and BA.5 can outcompete BA.2.12.1, the highly contagious strain that is currently the leading cause of COVID-19 infections in the US. .USA

These branches of the omicron variant family tree rose to prominence at about the same time;

BA.2.12.1 quickly took hold in the United States, while subvariants BA.4 and BA.5 established themselves in South Africa.

The subvariants share some similarities, such as changes in their genome location 452, a genetic address known to help the variants evade our immunity.

Viruses prepare for the fight

"It's like boxing," said Dr. Alex Greninger, deputy director of the clinical virology laboratory at the University of Washington.

"It's like the national champion of South Africa taking on the national champion of the United States. You don't know how to rank them if they've never wrestled," he says.

But the BA.4 and BA.5 subvariants have clashed with BA.2.12.1 in other parts of the world, such as the UK.

There, the scientists found that the time it took for the number of infections caused by a variant to double was about 5½ days for BA.2.12.1 and one day less for sub-variants BA.4 and BA.5, indicating that spread faster.

The doubling times were included in a recent technical report from the UK Health Security Agency.

"The favorite bet now suggests that BA.4 and BA.5 could end up with BA.2.12.1," Greninger said.

• New versions of the omicron variant outperform the BA.2 subvariant

Ho and his team think they have figured out what gives BA.4 and BA.5 an extra edge.

In addition to all the changes to other omicron subvariants that help them get rid of our vaccines, these viruses have introduced an F486V mutation.

This is a big change that helps them hide from our immune system.

In the past, it had a downside: It made the virus spike less able to bind to our cells, so they were less competitive.

But BA.4 and BA.5 have an additional mutation, called R493Q, that resets their ability to bind to cells, restoring their ability to infect us.

Although sub-variants BA.4 and BA.5 seem capable of out-competing BA.2.12.1, they have not met in the US, and the fitness of these strains is highly dependent on the playing field.

Variants do not follow the rules.

But for the next few months, according to experts, there will be a lot of covid-19 around us.

"By summer, going into winter, I anticipate these viruses to be out there at relatively high levels," Greninger said.

"Just the number of cases, just the workforce disruptions, it's a very high burden of disease."

coronavirus variants