The new omicron variant of COVID-19 has nearly made delta obsolete, as it was responsible for 95.4% of all new cases in the week that ended Jan. 1, according to CDC data released Tuesday. It took only about a month for the new variant to displace delta, as the first case of omicron was detected in the United States on Dec. 1 and it was responsible for just 0.6% of new cases for the week that ended Dec. 4. Omicron was responsible for 8% of cases by Dec. 11, 37.9% of cases by Dec. 18, and 77% of cases by...