S&P stumbles as Moderna sinks

The S&P 500 closed lower on Tuesday, as investors focused on a report questioning Moderna's recent coronavirus vaccine early-stage trial results, wiping out modest gains on the benchmark index in the last hour of trading.

Major averages fell to session lows in the wake of a report from STAT News that questioned the validity of the results of Moderna's vaccine trial, which the company had announced Monday. Moderna Inc shares plunged after the report, and closed down 10.41%.

"The market is keen on health-care news much more than it is on economic data," said Art Hogan, chief market strategist at National Securities in New York. "We are largely baking in the second quarter being down significantly - GDP growth rates, earnings, economic data - but what we don't know, what will drive markets will be incrementally good news on the healthcare front."

Stocks had initially edged higher as investors attempted to glean information from a mixed bag of results from major retailers.

Home improvement chain Home Depot fell 2.96% after it missed quarterly profit estimates due to higher costs, while department store operator Kohl's Corp tumbled 7.65% after reporting a bigger-than-expected loss.

Walmart Inc, on the other hand, exceeded expectations for quarterly revenue and earnings as online sales soared as consumers stockpiled essentials in response to coronavirus lockdowns. Still, its shares finished 2.12% down after rising as much as 3.4% earlier.

Advance Auto Parts climbed 3.59% after the company said same-store sales improved significantly at the start of the second quarter.

Trillions of dollars in fiscal and monetary stimulus have helped the S&P 500 rebound nearly 35% from its March 23 intraday low. While the benchmark index is now less than 13% below its Feb. 19 closing record, gains have largely slowed in May on uncertainty over truly halting the spread of the coronavirus and allowing business to resume and rising US-China tensions.

The Dow Jones Industrial Average fell 390.51 points, or 1.59%, to 24,206.86, the S&P 500 lost 30.97 points, or 1.05%, to 2,922.94 and the Nasdaq Composite dropped 49.72 points, or 0.54%, to 9,185.10.

Declining issues outnumbered advancing ones on the NYSE by a 1.43-to-1 ratio; on Nasdaq, a 1.63-to-1 ratio favored decliners.

The S&P 500 posted 11 new 52-week highs and no new lows; the Nasdaq Composite recorded 60 new highs and seven new lows.

Volume on US exchanges was 10.66 billion shares, compared to the 11.34 billion average for the full session over the last 20 trading days.