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Press Conference.

Disclosures: Fauci and Walensky report no relevant financial disclosures.
December 15, 2021
2 min read

Omicron cases will ‘continue to grow in the coming weeks,’ CDC director warns


Press Conference.

Disclosures: Fauci and Walensky report no relevant financial disclosures.
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The COVID-19 omicron variant, which has been in the United States since at least mid-November, has now been confirmed in at least 36 states and more than 75 countries, CDC Director Rochelle P. Walensky, MD, MPH, said Wednesday.

According to Walensky, early data suggest omicron is more transmissible than the delta variant, with cases doubling every 2 days.

 Source: Adobe Stock
Source: Adobe Stock.
Rochelle P. Walensky

“In looking at early data on transmissibility of omicron from other countries, we expect to see the proportion of omicron cases here in the United States continue to grow in the coming weeks,” Walensky said during a White House COVID-19 briefing.

Currently, about 96% of the nation’s new cases care are caused by the delta variant, but omicron already accounts for about 3% of cases — an increase from 0.1% last week.

In some areas of the country, omicron transmission is even higher. In New York and New Jersey, for example, the CDC estimates that 13% of cases are being caused by omicron, Walensky said.

A CDC report published last week showed there was not much severe disease reported among the first 43 patients in the U.S. with an identified omicron infection. Only one was hospitalized and none died. But it also showed that prior immunization did not prevent infection, as nearly 80% of the patients were fully vaccinated, including almost one-third who had received a booster shot.

Still, National Institute of Allergy and Infectious Diseases Director Anthony S. Fauci, MD, on Wednesday emphasized the effectiveness of COVID-19 vaccine booster doses, especially against variants of concern such as omicron.

Pfizer and BioNTech recently announced findings from an initial lab study showing that protection against omicron was improved after a third dose of their vaccine.

Anthony S. Fauci

“Our booster regimens work against omicron,” Fauci said during the White House briefing. “At this point, there is no need for a variant-specific booster.”

Fauci presented some omicron-specific data, including one study from Rockefeller University that showed “omicron exhibits a rather profound degree of neutralization escape,” he said.

“However, the two-dose mRNA-vaccinated people who received a booster dose [have] a substantial increase in neutralizing activity to the tune of a 38-fold increase,” Fauci said.

In a clinical study that observed the effectiveness of the two-dose primary Pfizer-BioNTech series against omicron, effectiveness dropped to about 33% from 80% in the pre-omicron era.

“But note that the effectiveness against hospitalization — which is critical — still maintains a 70% effectiveness,” Fauci said.

According to Walensky, the CDC will release data on Thursday that will “provide a snapshot” of national and state-level data on COVID-19 vaccine and booster effectiveness among residents of long-term care facilities.