The Centers for Disease Control and Prevention (CDC) on Tuesday significantly revised downward the estimate of the percentage of new COVID-19 infections in the U.S. caused by the omicron variant of the virus. According to agency data, omicron accounted for about 59 percent of all U.S. infections as of Dec. 25. Previously, the CDC said the omicron variant comprised 73 percent of all cases for the week ending Dec. 18. But that number has now been revised to 22.5 percent of all cases....