An afternoon slump left stock indexes broadly lower on Wall Street, erasing early gains, as traders worried anew about the rapid spread of the coronavirus in the U.S.

The S&P 500 lost 1.2%. It was up 0.3% in morning trading and small-company stocks were headed for another record high after Pfizer and BioNTech reported updated data suggesting their potential COVID-19 vaccine may be 95% effective.

Major indexes turned lower in afternoon trading, and the losses accelerated after New York City said it would close its public schools to in-person learning again as infections continue to rise there.