Omicron coronavirus subvariants BA.4 and BA.5 are now accounting for an estimated 35 percent of US cases, according to the Centers for Disease Control

BA.4/BA.5 will soon be dominant in the US. Here’s what that means

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2022-06-24 00:00:06

Omicron coronavirus subvariants BA.4 and BA.5 are now accounting for an estimated 35 percent of US cases, according to the Centers for Disease Control and Prevention. The subvariants are on a course to reach dominance at a faster clip than the subvariants before them, including the current reigning subvariant, BA.2.12.1, which is now in decline.

The pair—which share the same mutations in their SARS-CoV-2 spike proteins but have differences elsewhere in their genomes—are expected to reach dominance "in a few weeks," Dr. Shishi Luo tells Ars. Luo is the head of infectious diseases at Helix, a California-based population genomics and viral surveillance company that works with the CDC to help track emerging coronavirus variants nationwide.

When BA.4 and BA.5 were first detected in South Africa in April, it quickly became clear that the two can evade immune responses from vaccination and past infection, even infection from previous omicron variants.

On Wednesday, researchers in Boston published data in the New England Journal of Medicine that reinforced those findings. The latest data found that people who had been vaccinated and boosted had 21-fold lower neutralizing antibody titers against BA.4 and BA.5 compared to levels against the original version of SARS-CoV-2. And those neutralizing antibody levels were also 3.3-fold lower compared to levels against BA.1. Likewise, in people who had previously been infected with BA.1 or BA.2 (most of whom had been vaccinated, too), neutralizing antibody levels against BA.4 and BA.5 were still nearly 3-fold lower than levels against BA.1.