Last week, newly released data from the U.S. Centers for Disease Control and Prevention showed the Omicron variant making up 73.2 percent of Covid-19 cases, but the agency has now significantly revised that figure.
Now, the CDC says the new variant made up only 22.5 percent of new cases during the week that ended Dec. 18. That figure jumped to 58.6 percent for the week ending Dec. 25.
CDC estimates of circulating variants including week of 12/25. Notably week of 12/18 estimate of Omicron revised from ~73% to 22.5% (just a tad different!).
— Jason Gallagher (@JGPharmD) December 28, 2021
Now saying 58.6% of variants are Omicron nationwide. 1/ pic.twitter.com/duYpLSEXQm
As the CDC collects more data, they can more accurately pinpoint the proportions of each variant throughout the country, according to Dr. Li Tang, an associate faculty member in the Department of Biostatistics at St. Jude Children's Research Hospital.
"Earlier, they probably relied on a small number of available sequences. It should be also noted, although the confidence interval now is narrower, the range is still big, covering from 41.5% to 74%, suggesting large uncertainty," Dr. Tang told Fox News Digital.
The new estimates mean that the delta variant was still dominant for most of December, though omicron has a slight edge now. (Fox News)
"CDC’s models have a range,” CDC spokesperson Jasmine Reed told Fox News. “We’re still seeing steady increase in the proportion of Omicron.”
"In some regions in the country, Omicron accounts for [approximately] 90 percent or more of cases," Reed added.
According to Dr. Jerome Adams, former U.S. surgeon general, the speed at which Omicron is spreading means the CDC's original estimate will likely be accurate in the next week or two.
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