Stocks fall after questions are raised about a virus vaccine’s trial

Stocks on Wall Street fell on Tuesday, giving up some of Monday’s gains as investors assessed economic warnings from the Federal Reserve chair, Jerome H. Powell, and Treasury Secretary Steven Mnuchin. Both had addressed Congress about their response to the coronavirus pandemic, and what was still to come from both the Fed and the Treasury.

Late in the day, shares of the drug company Moderna slid after the medical-news website Stat questioned the robustness of its early stage trial of a coronavirus vaccine. Moderna’s announcement on Monday that the vaccine had shown some progress had helped set off a market rally of more than 3 percent — the best daily performance for the S&P 500 in six weeks.

But Stat, citing vaccine experts, said the information released by Moderna on Monday was not detailed enough to know if the vaccine was as promising as it might have seemed. Moderna’s shares fell more than 10 percent.

Reference: New York Times