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Hi, and welcome to COVID Quickly, a scientific American podcast series.

This is your fast track update on the COVID pandemic. We bring you up to speed on the science behind the most urgent questions about the virus and the disease.

We demystify the research and help you understand what it really means.

I'm Tony Lewis. I'm Josh Fishman.

And we're scientific American senior health editors.

Today we'll look at how new Omicron sub variants are already increasing cases and hospitalizations.

And we'll try and figure out if fall vaccine boosters should contain standard Omicron or some of those new sub variants instead.

It's the height of summer here, and we were kind of hoping for a break, but we're already seeing another COVID surge.

This time it's driven by Omicron sub variants BA5 and BA4. What do we know about them so far?

Yeah, Josh. Well, unfortunately the low after the last surge didn't last very long.

BA4 and BA5 are offshoots of the Omicron variant, a version of which caused a massive wave earlier this year.

BA5 and to a lesser extent BA4 now make up more than 70% of COVID infections in the U.S.

And they are the most capable of evading our immune response from vaccination or infection of any variant so far.

Now you have me worried. Do we know if these sub variants are causing more severe disease?

Well, we do know that we're seeing upticks and hospitalizations in countries around the world, including here in the U.S.

The variants appeared to cause more severe disease in hamsters, but there's not yet clear evidence of this in people.

But the more people who get infected, the more people who will end up in the hospital. It's just numbers.

Right, even if the portion of severe disease stays the same, the absolute number will climb along with these infections.

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