US shares were higher an hour into trade Thursday after the European Central Bank announced a larger-than-expected stimulus plan to fend off slow growth and deflation in the eurozone.
The Dow Jones Industrial Average added 52.08 points (0.30 percent) at 17,606.36.
The broad-based S&P 500 rose 8.75 (0.43 percent) to 2,040.87, while the tech-rich Nasdaq Composite gained 15.08 (0.32 percent) at 4,682.50.
ECB chief mario Draghi announced a 60 billion euro-a-month ($69 billion) bond buying program aimed at sparking more investment and growth in the eurozone, 10 billion euros more than markets expected.
"The ECB's actions will increase liquidity in the economy by giving bond holders liquid cash in place of less liquid bonds," said Carl Weinberg, chief economist at High Frequency Economics.
"What happens to this liquidity will determine the outcome of this exercise. It could go into stocks or bonds, or housing... or be spent on Blu-rays and cars. It could go into the US Treasury market, with its higher yields and appreciating currency. In that case, the euro will cheapen and yields in the United States will go down."
Earnings reports had a larger impact on trade. American Express shares lost 4.5 percent despite a solid fourth quarter, with investors apparently spooked by a rise in expenses and previsions. The bank and credit card issuer said it would lay off 4,000 workers to cut costs.
Rival Visa lost 1.0 percent.
Verizon sank 2.5 percent as it turned in a loss for the quarter, due to pension and other employee-related costs.
Airline United Continental pushed up 5.0 percent, driven by a strong forecast for earnings this year even as it missed expectations in the fourth quarter.
In the tech sector, memory specialist SanDisk's shares tumbled 4.7 percent on its earnings disappointment, while eBay jumped 3.8 percent.
Bond prices fell. The yield on the 10-year US Treasury rose to 1.87 percent from 1.85 percent Wednesday, while the 30-year jumped to 2.46 percent from 2.44 percent. Bond prices and yields move inversely.