Stocks have their biggest gain in weeks as Wall Street is encouraged by a vaccine prospectvaccine prospect. Many of the world’s economies have begun to loosen restrictions on commerce, the Federal Reserve chair on Sunday signaled that the central bank has more firepower to lend to recovery efforts, and a drugmaker reported positive developments in an early trial of a coronavirus vaccine.
Taken together, the developments set off a surge in global stock prices and Wall Street had its best day in about six weeks.
The S&P 500 rose more than 3 percent Monday, while stock benchmarks in Europe were 4 percent to 6 percent higher.
Before trading began in the United States, the drugmaker Moderna said its coronavirus vaccine showed promising early results in tests on humans. The early-stage tests were on just eight people, but the hope that a vaccine might be quickly developed was enough to give stock prices a lift.
Also bolstering markets was a pledge from Jerome H. Powell, the Fed chair, that there was “really no limit” to what the central bank could do with its emergency lending facilities.
“The one thing I can absolutely guarantee is that the Federal Reserve will be doing everything we can to support the people we serve,” Mr. Powell said during a television interview broadcast on Sunday.
The Fed chair also suggested that the worst economic readings were yet to come, even as states begin to gradually reopen. He said that he expected “a couple more months” of job losses and acknowledged that the unemployment rate, which hit 14.7 percent in April, could peak at 20 percent or even 25 percent.
Still, investors were looking for silver linings as the world grapples with lockdowns and other restrictions. Japan released economic figures on Monday that showed its economy formally fell into recession, but Tokyo has begun easing some of its containment efforts. Some restrictions have also been lifted in parts of Europe and the United States.
And trading on Monday had all the characteristics of a rally focused on the prospects for a return to normal. Shares of companies that stand to gain the most, like United Airlines, Expedia Group and Marriott International, were among the best performers in the S&P 500.
Businesses that have benefited as Americans stockpiled food and cleaning supplies, like Campbell Soup and Clorox, were among a small number of decliners.
Oil prices also reflected optimism about the economy, with West Texas Intermediate, the U.S. benchmark, rising above $30 a barrel for the first time since March. Shares of energy companies like Chevron and Exxon were also sharply higher.