CDC reduces estimates of Omicron variant among US Covid-19 cases

“We had more data come in from that timeframe, and there was a reduced proportion of Omicron,” a CDC spokesperson said. “It’s important to note that we’re still seeing a steady increase in the proportion of Omicron.”

The fast-spreading variant was first detected in southern Africa and Hong Kong in November, with the first known case in the United States identified on Dec 1, in a fully vaccinated person who had traveled to South Africa.

Since then, the strain has rapidly spread across the world and driven a surge in US infections, causing widespread flight cancellations and dashing hopes for a more normal holiday season.

The Delta variant, which had been the dominant strain in the past few months, accounts for 41.1% of all US Covid-19 cases as of Dec 25, the public health agency’s data proportions showed.

Former US Food and Drug Administration Commissioner Scott Gottlieb said on Twitter that if the CDC’s new estimate of Omicron prevalence was precise, then it suggests that a good portion of the current hospitalisations may still be driven by Delta infections.

The agency said the data includes modeled projection that may differ from weighted estimates generated at later dates.