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The omicron variant may be the most infectious one yet

ARI SHAPIRO, HOST:

The discovery of a new coronavirus variant called omicron has put the globe on alert. The World Health Organization said today that the variant poses a very high risk. It's been found in more than a dozen countries. It was only detected last week by scientists in Botswana and South Africa, but there's evidence that it's been spreading rapidly across the southern part of the continent. And there are several red flags that this variant may be the most infectious one yet. NPR's global health correspondent Michaeleen Doucleff is here. And, Michaeleen, what are those red flags?

MICHAELEEN DOUCLEFF, BYLINE: So the thing is, Ari, that South Africa until recently had very low numbers of COVID cases. They were in this lull. And then all of a sudden, there was a burst of cases around Pretoria among college students. And at first, scientists thought this was just delta, you know, starting another surge. But to make sure, they sequenced it, and it wasn't delta at all.

SHAPIRO: And reporting has shown it was the omicron variant.

DOUCLEFF: That's right. It was this totally new variant with its extraordinary number of mutations. For instance, in the region that binds to human cells - just that region - delta has two mutations. Another concerning variant, beta, has three. Omicron has 10 - 10 mutations.

SHAPIRO: Ten - that sounds like a much higher number than the others.

DOUCLEFF: Yes, it's a big jump. And in a period of about two weeks, this variant has spread to seven of the nine provinces in South Africa, basically across the whole country. Tulio de Oliveira is one of the first scientists to sequence this variant. He's a bioinformatician at the Center for Epidemic Response and Innovation in Durban.

TULIO DE OLIVEIRA: We can see that variant potentially spreading very fast. As the minister of health highlight, the number of cases really coming very fast. And we do expect, unfortunately, to see pressure in the health care system in the next few days and weeks.

DOUCLEFF: Now remember, delta is also circulating in South Africa, so it's not just that omicron is spreading quickly there. It is - it also seems to be outcompeting delta.

SHAPIRO: What's the significance of that? What does it mean that the one variant is outcompeting the other?

DOUCLEFF: Well, it looks like, at least in South Africa, that omicron has some advantage over delta, some property that's making it spread much more easily. I was talking to Jeremy Luban about this. He's a virologist at the University of Massachusetts Medical School.

JEREMY LUBAN: The bottom line with this creature is, is it more transmissible than delta? And I think the fact is, nobody knows, but it looks like it could be much more.

DOUCLEFF: To date, delta has been the most contagious variant we know about. You know, within about nine months, it swept through the continents, pushing out all the other variants, causing these huge surges. So being more contagious would be quite remarkable. But as Luban points out, there isn't a lot of data yet to measure transmissibility, and what data is there could be skewed. It's dominated by this very specific cluster of students in Pretoria. But that being said, the mutations in omicron do suggest it is quite contagious.

SHAPIRO: OK. So whether it's transmissible is one big concern. What are the other red flags?

DOUCLEFF: So the WHO says there's preliminary evidence that omicron can more easily reinfect people, cause second infections. So it looks like all those people who already had COVID could once again be vulnerable because if you look at the mutations in omicron, they strongly suggest the variant would be very good at sneaking past the immune system. Paul Bieniasz is a virologist at Rockefeller University. He and his colleagues have already studied some of these mutations in the lab and found that they can prevent antibodies from killing the virus.

PAUL BIENIASZ: So based on that, we expect that omicron will be significantly resistant to antibodies that are circulating in individuals who are convalescent or who have had mRNA vaccines.

SHAPIRO: To be clear, is what he's saying there that the vaccines may not be as effective against this variant?

DOUCLEFF: Yes. So Bieniasz predicts from his work in the lab that they may not be as effective. But based on his data, he says that you can increase that effectiveness by getting three doses of the vaccine. That seems to broaden out your defenses.

SHAPIRO: What about people who have had COVID-19 but have not received the vaccine? Could the vaccines help protect them against getting infected again with the omicron variant?

DOUCLEFF: Yes, absolutely - you know, for sure. What is becoming clear here is that multiple exposures via the vaccine, via boosters gives you the best protection, really, against any of the variants.

SHAPIRO: NPR global health correspondent Michaeleen Doucleff. Thank you.

DOUCLEFF: Thank you, Ari. Transcript provided by NPR, Copyright NPR.

Michaeleen Doucleff, PhD, is a correspondent for NPR's Science Desk. For nearly a decade, she has been reporting for the radio and the web for NPR's global health outlet, Goats and Soda. Doucleff focuses on disease outbreaks, cross-cultural parenting, and women and children's health.