TOKYO (Reuters) - Oil prices were mixed on Friday in quiet trade due to the U.S. Thanksgiving holiday, with West Texas Intermediate (WTI) dropping more than 1% amid concerns about oversupply and doubts about a vaccine to end the coronavirus pandemic. WTI was down by 69 cents, or 1.5%, at $45.02 by 0104 GMT. U.S. crude prices did not settle on Thursday due to the holiday. Brent crude was up by 9 cents at $47.89, having fallen 1.7% overnight. Both benchmarks have risen about 6% this week, after AstraZeneca earlier announced that its COVID-19 vaccine could be up to 90% effective, adding to successful trial results of two others under development in the fight to end the worst pandemic in a century. But questions have been raised over the so-called “vaccine for the world” as several scientists have sounded doubts over how robust the results of the trials were. “It seems some profit taking is finally kicking in ... as we ease into the end of the week,” Craig Erlam, senior market analyst at OANDA. Still, “with WTI holding above $45 and Brent having touched $49, it seems crude is through the worst of its post-summer troubles,” he said. The Organization of the Petroleum Exporting Countries (OPEC) and other producers including Russia that make up the OPEC+ grouping are leaning towards delaying next year’s planned increase in oil output, three sources close to OPEC+ said. OPEC+ was planning to raise output by 2 million barrels per day (bpd) in January - about 2% of global consumption - as it moves to ease this year’s record supply cuts. But rising Libyan output is contributing to concerns about oversupply in the market as many people are ignoring lockdown advice and travelling. Nearly 6 million Americans took air trips from Friday to Wednesday in advance of the Thanksgiving break as they ignored advice from the Centers for Disease Control to stay home, the U.S. Transportation Security Administration said.