The blue-chip Dow hit an all-time high on Thursday, extending a record-setting run as a dip in weekly jobless claims allayed fears over the economic damage from a rampant surge in COVID-19 infections in the United States.
Financials, materials, and energy sectors, which tend to benefit in an environment of improving economic outlook, led gains among nine of the 11 major S&P 500 sector indexes trading higher.
The Labor Department's data showed that the number of Americans filing for new unemployment claims slipped to 198,000 in the Christmas week from 205,000 a week earlier. Economists polled by Reuters had forecast 208,000 applications for the latest week.
Equities have rallied recently, albeit in some of the thinnest trading volumes that US stock exchanges have seen this year, as growing evidence emerged that the Omicron variant causes less severe illness than the Delta strain.
Dow eyes record highs in thin holiday trade; retailers jump
Aiding sentiment, top US infectious disease adviser Dr. Anthony Fauci said on Wednesday the surge in cases of the Omicron coronavirus variant in the United States is likely to peak by the end of January.
"You've seen a microcosm of the market rally all year in this week - really strong GDP numbers, employment numbers and really skeptical investors who have kept a nice lid but the market keeps scratching higher," said Carol Schleif, deputy chief investment officer at BMO Family Office.
"It is a classic example of a wall of worry that the market is climbing and we suspect that it'll take that into the new year as well."
As Wall Street's main indexes look to exit the year with their sharpest three-year surge since 1999, the attention will shift towards the pace of US interest rate hikes in the face of soaring prices and supply chain logjams.
At 9:43 a.m. ET, the Dow Jones Industrial Average was up 137.58 points, or 0.38%, at 36,626.21, the S&P 500 was up 5.88 points, or 0.12%, at 4,798.94, and the Nasdaq Composite was down 0.81 points, or 0.01%, at 15,765.40.
Stock markets are currently in a historically strong period, also called the "Santa Claus Rally" that typically occurs in the last five trading days of the year and the first two of the new year.
Among individual stocks, Biogen Inc slipped 6.1%, giving back some gains from the prior session as Samsung BioLogics denied a media report that said the South Korean firm was in talks to buy the US drugmaker.
Advancing issues outnumbered decliners by a 3.06-to-1 ratio on the NYSE and by a 2.72-to-1 ratio on the Nasdaq.
The S&P index recorded 47 new 52-week highs and no new low, while the Nasdaq recorded 36 new highs and 76 new lows.