(Bloomberg) — U.S. stocks fell for the first time in four sessions after reports circulated that Moderna Inc.’s vaccine study, which was credited in part for Monday’s rally, didn’t produce enough critical data to assess its success. Crude oil and Treasuries gained.The S&P 500 and Nasdaq Composite turned negative in the last hour of trading, while the Dow Jones Industrial Average extended its losses. Equities had fluctuated much of the day after optimism over the drug as a potential coronavirus vaccine sent the S&P up the most Monday in almost six weeks. Crude oil rose for a fourth day.“We’re going to continue to see volatility because every day the market’s taking any little piece of information it has about things and prices it in,” said Peter Mallouk, president and chief investment officer of Creative Planning. “Every day it’s taking every little piece of information and it’s instantly pricing it in. Everything else is a derivative of Covid-19 now.”Earlier, Federal Reserve Chairman Jerome Powell reiterated during a Senate hearing that the central bank is ready to use all the weapons in its arsenal to help the U.S. economy endure the coronavirus pandemic.The Stoxx Europe 600 Index retreated as investors showed little reaction to both news of a $546 billion recovery fund for the region and a surprise jump in German investor confidence. European government bonds were mixed. Sterling strengthened after the U.K. announced plans for 30 billion pounds ($37 billion) in tariff cuts after Brexit.Riskier assets had started the week on the front foot after the Moderna news fueled hopes for a coronavirus vaccine, but investors are struggling to maintain the optimism as they continue to monitor efforts to both contain the pandemic and restart economies.“A vaccine would be a bullish game changer, and stocks reacted accordingly,” Tom Essaye, author of “The Sevens Report” newsletter, wrote in a note. “But one day doesn’t make a sustainable move.”Headwinds remain for stocks, not least a deteriorating U.S.-China relationship. In a further sign of tightening scrutiny on capital flows to the Asian nation, Nasdaq is set to unveil new rules for initial public offerings including tougher accounting standards that will make it more difficult for some Chinese companies to list on the exchange.Asian equities rallied, tracking the big gains on Wall Street from a day earlier.These are some of the main moves in markets:For more articles like this, please visit us at bloomberg.comSubscribe now to stay ahead with the most trusted business news source.©2020 Bloomberg L.P.