The S&P 500 was up 1.1% to 2,075.04 in midday trading.
The Dow Jones Industrial Average was up 1.1% to 17,938.60 and the Nasdaq was up 1% to 4,919.58.
The yield on a 10-year Treasury bond fell 1.23% to 2.09%.
The price of gold rose 0.1% to $1,153.90.
Irvine-based Edwards Lifesciences Corp. was up 10.2% to $149.10 and a $16.1 billion market cap on positive results from a study of a competitor’s heart-valve. Medtronic PLC’s CoreValve showed a relatively low rate of strokes or heart attacks in a study in Denmark. The results were recently presented to an American College of Cardiology conference, and provided a general lift to makers of non-invasive heart valves, including Edwards’ Sapien.
Irvine-based Habit Restaurants Inc. was up 3.6% to $31.04 and an $808 million market cap. Shares made up ground lost on Friday when the fast-casual burger chain said its shareholders would sell 5.75 million shares in the company.