BA.5, now dominant U.S. variant, may pose the biggest threat to immune protection yet

BA.5, now dominant U.S. variant, may pose the biggest threat to immune protection yet The FDA recommended that Covid vaccine makers target two omicron subvariants — BA.4 and BA.5 — in new booster shots expected to come this fall. NBC News

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The coronavirus subvariant known as BA.5 accounted for nearly 54% of the country's Covid cases as of Saturday, according to the Centers for Disease Control and Prevention. A similar subvariant, BA.4, makes up 17% more.

"They're taking over, so clearly they're more contagious than earlier variants of omicron," said David Montefiori, a professor at the Human Vaccine Institute at Duke University Medical Center.

The two subvariants also appear to evade protection from vaccines and previous infections more easily than most of their predecessors.

Montefiori estimated that BA.4 and BA.5 are about three times less sensitive to neutralizing antibodies from existing Covid vaccines than the original version of the omicron variant, BA.1. Other research suggests that BA.4 and BA.5 are four times more resistant to antibodies from vaccines than BA.2, which replaced the omicron variant as the U.S.'s dominant version of the coronavirus in April.

Francois Balloux, the director of the University College London Genetics Institute, said that's most likely another reason the subvariants have taken over.

"At this stage now, I think all these variants actually are roughly equally transmissible, so there’s not a huge difference," he said."It’s just some are slightly better at infecting people who have been vaccinated or infected by previous variants." ...