CDC lowers estimate of COVID-19 Omicron infections to 59.6% of total cases

Dec. 28 (UPI) -- The U.S. Centers for Disease Control and Prevention on Tuesday revised down the estimate of the percentage of new COVID-19 infections caused by the Omicron variant.

Agency data shows that Omicron accounted for 58.6% of U.S. COVID-19 infections the week ending Dec. 25. The agency also dramatically lowered its estimate of Omicron's prevalence for the week ending Dec. 18, from 73% of all cases down to 22.5%.

CDC representative Jasmine Reed told Politico that the disparity was a result of the rate at which Omicron infections spread.

"There was a wide predictive interval posted in last week's chart, in part because of the speed at which Omicron was increasing," Reed said. "We had more data come in from that timeframe and there was a reduced proportion of Omicron."

The CDC's model showed that the Delta variant accounted for 41.1% of U.S. infections as of Dec. 25.

"Setting aside the question of how the initial estimate was so inaccurate, if CDC's new estimate of Omicron prevalence is precise then it suggests that a good portion of the current hospitalizations we're seeing from COVID may still be driven by Delta infections," former Food and Drug Administration Commissioner Scott Gottlieb tweeted Tuesday.

The United States reported a seven-day moving average of more than 240,000 daily COVID-19 cases Monday, up from 150,000 a week prior, according to the CDC. There have been more than 1,000 daily COVID-19 for most of December, as well.

"It's important to note that we're still seeing steady increase in the proportion of Omicron," Reed said.

The news comes after the CDC on Monday also cut its recommended period of isolation for asymptomatic people who have tested positive for COVID-19 from 10 days to five days.