RALEIGH, N.C. (WNCN) — The Centers for Disease Control and Prevention now says there was much less of the omicron COVID-19 variant circulating earlier this month than the agency originally thought.

The CDC originally estimated that omicron made up 73 percent of the samples sequenced during the week that ended Dec. 18 — but later revised it to just 23 percent.

How could those estimates have been so far off?

Dr. Thomas Denny, the chief operating officer of the Duke Human Vaccine Institute, says it was a result of more data flowing to the CDC, which changed those estimates to keep up with the science.

“I don’t see this as getting something wrong,” Denny said. “You’re getting information by the minute, by the hour, and you’re trying to make decisions, and then you’re trying to also extrapolate as to where we’re going to be next week or two weeks out.”

He cautions people against overreacting to the update and says the agency likely tried to draw too many conclusions from too small of a sample size of data.

“I think what they probably did was, they looked at what numbers they were seeing over a couple-day period, and then extrapolated,” Denny said. “You’ve got to be very careful when you’re extrapolating from a short period of time.”

The change aligns the national figures with what has been observed locally.

The sequencing lab at the University of North Carolina says omicron made up more than 20 percent of the samples it checked last week — up drastically from its 2.8 percent share a week earlier.

At the state level, the Department of Health and Human Services releases its breakdown of variants every Thursday. The most recent numbers, which covered the week ending Dec. 11, showed omicron making up less than 5 percent of the samples from that week.

(Source: NCDHHS)

And while the CDC’s estimates from two weeks ago were lowered, the trend remains the same: omicron’s share is growing, up to 59 percent of the samples from last week.

In other words, delta may still be the dominant strain — but not for long.

“I don’t think any of us are thinking that we’re not going to see 100 percent conversion from delta very soon,” Denny said. “That’s the direction we’re going in.”

Knowing the variant can be important because it can affect how the disease is treated. Some monoclonal antibody treatments are less effective against omicron, which Denny said has evolved to be less affected by those therapies.

“The monoclonal antibodies that do treat this new variant are sort of on a rationing,” he said. “So it’s important that we track it and then we can say, ‘Well, we’re seeing an increase and we will most likely need to have access to that other therapy.’”


CBS 17’s Joedy McCreary has been tracking COVID-19 figures since March 2020, compiling data from federal, state, and local sources to deliver a clear snapshot of what the coronavirus situation looks like now and what it could look like in the future.