WASHINGTON – A few weeks after millions of Americans traveled for Thanksgiving, the omicron variant is emerging as many more people begin to set out for Christmas and New Year's, worrying public health officials and complicating travel plans. The end-of-year rush – typically the busiest holiday travel period of the year – will occur as researchers scramble to fully understand the new coronavirus variant's transmissibility, severity and defenses against vaccines. But travel watchers say they expect confidence in vaccines and booster shots, coupled with mounting pandemic fatigue after almost two years, will keep millions traveling over the winter holidays despite the increased uncertainty. Rishabh Chauhan, a University of Illinois at Chicago doctoral candidate studying public risk perception and behavior during the pandemic, said early reports of the variant appearing to be more transmissible but less dangerous probably will leave most holiday travel plans intact. "We think omicron might put a small dent in travel, but we haven't heard about any mass cancellations," Chauhan said. "But we're living in very uncertain times. News is coming out every day, so it's shaky to talk about the future." With many travel plans still a week away, and medical research findings emerging daily, Chauhan and other experts say it's difficult to forecast the variant's effects on pent-up demand for holiday travel. "Delta gave a body blow to air travel, and now with omicron there's a great deal of speculation of what it means," said Sheldon H. Jacobson, a professor of computer science at the University of Illinois at Urbana-Champaign who uses data modeling to analyze the impact of the virus on the aviation system. "Until more data is available, it's hard to predict." The travel industry is coming off a big Thanksgiving bounce, signaling that many travelers will tolerate a certain amount of risk. Air travel over the 10-day holiday period more than doubled compared with 2020, according to the Transportation Security Administration (TSA). The 21 million people screened at security checkpoints amounted to more than 90% of pre-pandemic levels. The more than 2.4 million screened the Sunday after Thanksgiving hit the highest daily tally since the pandemic began, according to TSA figures.