The blue-chip Dow was on track for its best one-day percentage gain since Nov. 9, 2020, with Boeing Co, providing the biggest lift. “Obviously, there’s concern about Omicron but there’s a feeling that infections aren’t as severe as initially thought,” said Oliver Pursche, senior vice president at Wealthspire Advisors, in New York. As world governments scramble to determine how to respond to the emergent COVID-19 variant Omicron, the United States is set to require private health insurance companies to provide at-home tests, a policy expected to go into effect on Jan. 15.