NEW YORK -- Stocks that traded heavily or had substantial price changes Thursday:

       Weibo Corp., down 17 cents to $24.51.

       The Chinese social media company announced a $500 million stock buyback plan.

       Novavax Inc., down $1.10 to $73.65.

       The vaccine maker asked European regulators to expand conditional approval of its COVID-19 vaccine to teenagers.

       Tempur Sealy International Inc., down $1.07 to $27.92.

       The mattress maker gave investors a discouraging sales update.

       Citigroup Inc., down $1.57 to $53.40.

       Bond yields fell and weighed down banks, which rely on higher yields to charge more lucrative interest on loans.

       Duke Energy Co., up 18 cents to $111.66.

       Some utility stocks eked out gains as investors shifted money into the sector, which is considered less-risky.

       Edwards Lifesciences, up 63 cents to $117.72.

       The medical device maker received U.S. regulatory approval for its Mitris Resilia heart valve.

       Walgreens Boots Alliance Inc., down $2.69 to $44.77.

       Investors were disappointed after the largest U.S. drugstore chain left its financial forecasts unchanged.

       Occidental Petroleum Corp., down 74 cents to $56.74.

       Energy stocks slipped along with falling crude oil prices.