The highly transmissible Omicron variant has rapidly taken hold in the United States and now accounts for nearly three-quarters of new Covid-19 cases nationwide, according to the Centers for Disease Control and Prevention.
CDC estimates on Monday showed that Omicron accounted for an estimated 73.2 percent of U.S. cases surveilled between Dec. 12 and 18, with the Delta variant now accounting for 26.6 percent of cases. Between Dec. 5 and Dec 11, Omicron accounted for just 12.6 percent of U.S. cases, the agency estimated.
CDC Director Rochelle Walensky and other health officials last week said the expectation was the variant would become the dominant strain in the coming weeks. The White House has urged vaccinations and booster shots to combat the new variant, and President Joe Biden is expected to amplify that message during a speech on the state of the pandemic on Tuesday.
Omicron has left the administration reassessing what it means to be fully vaccinated and on how to prepare the public for the possibility of needing a fourth shot. Some projections say that daily cases could surge to two to three times what the country was hit with during the Delta variant surge.
Internal HHS modeling on testing demand circulated earlier this month estimated Omicron would become dominant within four weeks. The modeling was based on assuming the variant is between three to five more times more transmissible than Delta. Testing demand could potentially triple over the next two months, health officials have warned privately.
HHS Secretary Xavier Becerra said that the administration is trying to move the conversation to focus on Covid-19 severity, not cases. Biden has warned of a “winter of severe illness and death” for the unvaccinated and that the vaccinated can largely avoid severe illness and death.