Despite sparking widespread concern across the world, it appears that the Centers for Disease Control and Prevention (CDC) overestimated the earlier spread of the Omicron variant of COVID-19 in the United States by more than 200%.

On December 20, the CDC reported that the vast majority (73%) of COVID-19 cases in the United States were Omicron cases, which was up by 0.7% compared to the previous two weeks. But the CDC has now walked back this number to 22.5%, not 73%. 

“The rapidly spreading omicron variant is now the dominant Covid strain in the U.S., representing 73% of sequenced cases, according to data published Monday by the Centers for Disease Control and Prevention,” CNBC reported on December 20. “Omicron has displaced the previously dominant delta variant, which the CDC says is now an estimated 26.6% of sequenced cases for the week ending December 18. Just one week earlier, delta made up 87% of cases to omicron’s 12.6%, the data shows.”

However, the CDC “significantly revised downward the estimate of the percentage of new COVID-19 infections in the U.S. caused by the omicron variant of the virus,” The Hill reported. As of Christmas, the CDC estimated that the number of new coronavirus cases attributable to Omicron was 58%. 

“There was a wide predictive interval posted in last week’s chart, in part because of the speed at which Omicron was increasing,” a CDC spokesperson told POLITICO. “We had more data come in from that timeframe and there was a reduced proportion of Omicron.”


“According to agency data, omicron accounted for about 59 percent of all U.S. infections as of Dec. 25. Previously, the CDC said the omicron variant comprised 73 percent of all cases for the week ending Dec. 18. But that number has now been revised to 22.5 percent of all cases,” The Hill reported. “The omicron variant is highly transmissible and spreading rapidly, resulting in surges of infections even among people who are vaccinated. However, people who are vaccinated, and especially those who have received booster shots, are well protected against severe disease from the variant, experts say, meaning it poses the greatest risk to the unvaccinated.”

Former Food and Drug Administration (FDA) Commissioner Scott Gottlieb argued that, even though the “initial estimate was so inaccurate,” the latest data indicates that “a good portion of the current hospitalizations we’re seeing from COVID may still be driven by Delta infections.”

According to the CDC, Omicron was first identified in South Africa, and “early evidence suggests that fully vaccinated people who become infected with the Omicron variant can spread the virus to others.”

“All FDA-approved or authorized vaccines are expected to be effective against severe illness, hospitalizations, and deaths,” the CDC added. “The recent emergence of the Omicron variant further emphasizes the importance of vaccination and boosters.”

The highly contagious Omicron strain was first detected in the U.S. on December 1 in a fully vaccinated person who had traveled to South Africa.

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