Federal health officials said on Monday that Omicron is more advanced than other variants and is now the predominant version of the coronavirus in the United States, responsible for 73% of new infections last week. US Centers for Disease Control and Prevention shows that the proportion of infected omicron cases increased about 6-fold in just one week.  In many of the countries it is even higher.

Omicron is estimated to be responsible for 90% or more of new infections in the New York region, southeast, industrial Midwest, and  Pacific Northwest. National rates suggest that there were more than 650,000 Omicron infections in the United States last week. Since the end of June, the Delta Variant has been the leading version of infectious diseases in the United States. As of the end of November, more than 99.5% of coronaviruses were delta viruses, according to CDC data. However, in less than a month, African scientists first warned about Omicron, and on November 26, the World Health Organization described it as a "worried variant." Since then, mutants have appeared in about 90 countries.  

Much is not known about the Omicron variant, such as whether it causes more or less serious illness. Early studies suggest that vaccinated people need boosters to best prevent Omicron infection, but even without boosters, vaccination should provide strong protection. Dr. Ameshua Dalha, Senior Scientist at the Centers for Health and Security in John Hopkins, said he was not surprised by the CDC data, given observations in South Africa, the United Kingdom, and Denmark, showing that Omicron is overtaking Delta.