What omicron's alarming spread means for the U.S.

MARY LOUISE KELLY, HOST:

The new coronavirus variant, omicron, has now shown up in about 60 countries, and the picture emerging in places like Europe is not good. There, omicron is spreading remarkably fast, and officials warn it could soon dominate. As NPR's Will Stone reports, scientists in the U.S. are watching closely.

WILL STONE, BYLINE: The first country to really get hit by omicron was South Africa. This was the end of November, and at the time, overall coronavirus cases were low there, as were vaccination levels. So the question became - would the variant also gain traction in a very different place where it has competition, both from a high number of delta cases and vaccination levels? Jeffrey Barrett says, so far, the answer seems to be yes.

JEFFREY BARRETT: I think it's very clear that omicron can grow fast and indeed faster than delta in countries with ongoing, substantial delta epidemics, which is what's happening in the U.K. and in Denmark.

STONE: Barrett directs the COVID-19 Genomics Initiative at the Wellcome Sanger Institute, which tracks variants in the United Kingdom.

BARRETT: We have not faced a situation where a new variant is growing this fast basically since the beginning of the pandemic.

STONE: And remember - back then, no one was immune. Omicron is still only a small portion of overall infections, but U.K. health officials warn that cases of the variant are doubling every few days and could make up half of all cases within a few weeks.

BARRETT: That's a realistic scenario, and it is striking and concerning.

STONE: And it's one the U.S. should prepare for. Barrett says what the virus does in Europe often foreshadows where the pandemic is headed on the other side of the Atlantic.

BARRETT: By next week, we will see clear evidence of the omicron wave in European countries, and I suspect the U.S. is, at most, a week behind that.

STONE: Early evidence suggests omicron spreads more than twice as quickly as delta. Nathan Grubaugh at the Yale School of Public Health says why omicron is more transmissible hinges on two questions - is omicron inherently more contagious, and is it better at escaping the immune defenses from either vaccination or prior infection?

NATHAN GRUBAUGH: Looking at these early omicron cases, what we've anticipated in immune escape is turning out to be true, and the transmissibility seems to be at least that of delta's.

STONE: This is all based on early evidence, like lab studies suggesting the vaccines aren't as effective at stopping omicron infections.

GRUBAUGH: It's just going to make it a more competitive virus in this landscape now where we have a lot of immunity.

STONE: Grubaugh says the vaccine likely still works against severe disease, but if it isn't great at preventing infections, that's a lot of people who can get sick in a place like the U.S. and a big advantage against delta. Wafaa El-Sadr of Columbia University says if all this holds up...

WAFAA EL-SADR: We would anticipate in the United States is that over time, it would become the dominant variant. Because it's always the more transmissible one that takes over.

STONE: But El-Sadr says it's still too early to know how quickly the virus will spread because a growing share of the population has booster shots. There are early indications that boosters do offer protection against infections.

EL-SADR: This in and of itself may very much influence the trajectory of omicron in a country like the United States versus in a country like South Africa.

STONE: But Matt Ferrari at Penn State University says we should let history be our guide here.

MATT FERRARI: So we don't necessarily know how bad the future is going to be. But more than any other point in the pandemic, we know how bad it could be.

STONE: Ferrari says, so far, there's no evidence that omicron causes more severe disease, although it's too early to make any pronouncements. But...

FERRARI: Even if it's the same level of disease severity or a little bit milder, if you multiply that by many, many more people getting infected, that can still be a significant burden.

STONE: A burden on hospitals that are dealing with a growing winter surge from the virus that's already here. Will Stone, NPR News.

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