U.S. stock indexes were mixed Tuesday, a day after a record close for the S&P 500 amid lower liquidity in the last days of the year.

The $S&P 500 index(.SPX.US)$ swung between small gains and losses, touching a new intraday high in morning trading, after the broad-market index rallied 1.4%on Monday. It finished down 4.84 points, or 0.1%, to 4786.35. The $Dow Jones Industrial Average(.DJI.US)$ rose 95.83 points, or 0.3%, to 36398.21. The $Nasdaq Composite Index(.IXIC.US)$ fell 89.5 points, or 0.6%, to 15781.72.

Stocks have been buffeted by the spread of the Omicron variant in recent weeks as governments around the world have imposed restrictions to try to curb coronavirus infections. But some recent studies have suggested the variant might result in milder illness with lower risk of hospitalization.

The Centers for Disease Control and Prevention reduced the recommended isolation period for some people who test positive to try to minimize disruptions. Still, many economists have lowered their forecasts for economic growth in the first quarter of next year.

"What is emanating from markets is the faith that Omicron won't be able to disrupt the economic recovery," said Antonio Cavarero, head of investments at Generali Insurance Asset Management. "There is no visible risk reduction." That is partly due to lower liquidity from fewer people working around the holidays, he said.

Stock investors are keeping eyes on a phenomenon known as the "Santa Claus Rally." Indexes such as the S&P 500 have a tendency to rise in the last five days of the year and the first two days of the new year. Such a rally takes place at the end of about four of every five years, according to the Stock Trader's Almanac.

"It happens because people start positioning. People are reading everyone's 2022 estimates and planning for next year," said Jeffrey Meyers, a consultant to hedge funds and family offices at Market Securities.

Governments and policy advisers are showing signs of taking a lighter touchwith policies regarding the rapidly spreading Omicron variant, reducing quarantine times and in some instances forgoing social-distancing restrictions as they try to keep economies moving. Vaccine makers gave up gains from earlier in the session, with $Novavax(NVAX.US)$ declining 1.2% and $Moderna(MRNA.US)$ down 2.2%.

The news has helped shares of travel and energy companies, with $United Airlines(UAL.US)$ up 1.6% and $Valero Energy(VLO.US)$ up 1.9%.

Cutting quarantine times is bullish for investors and prompting market participants to look beyond the Omicron surge, said David Kotok, chief investment officer at Cumberland Advisors. But it also risks allowing the Covid-19 virus to mutate, spread and disrupt economies, he added. He is overweight healthcare stocks.

"This ain't over, and markets want to celebrate it being over. But the virus doesn't care about markets want," Mr. Kotok said.

Oil prices ticked up, with global benchmark Brent crude climbing 0.4% to $78.94 a barrel.

The yield on the benchmark 10-year Treasury note was unchanged at 1.480%.

The S&P CoreLogic Case-Shiller National Home Price Index, which measures average home prices in major metropolitan areas across the nation, showed U.S. home-price growth slowed in October. Shares of home builders edged higher during Tuesday's session, with $D.R. Horton(DHI.US) advancing 0.7% and $Taylor Morrison Home(TMHC.US)$ rising 0.8%.

U.S. companies will be entering 2022 at a very high level of corporate earnings, said Mr. Kotok. That will require companies to produce robust earnings growth next year, in the face of less fiscal and monetary policy stimulus.

「I'm a terrified bull,」 he said.

$Bitcoin(BTC.CC)$ slipped around 6.3% from its level at 5 p.m. ET on Monday, trading around $47,794. The cryptocurrency has oscillated around the $50,000 mark for the past five days.

Overseas, the pan-continental Stoxx Europe 600 added 0.6%.

The Turkish lira rose 1.3% to 11.8 to the dollar. The currency had strengthened after the government announced a new economic plan last week. President Recep Tayyip Erdogan 「may have bought Turkey some time but it’s still not a great story,」 Mr. Meyers said. Speculative investors likely closed out short positions ahead of the long holiday weekend and may now be putting them back on, weighing on the lira, he said.

In Asia, most major benchmarks rose. The Shanghai Composite Index climbed 0.4% and Hong Kong's Hang Seng Index added 0.2%. Japan's Nikkei 225 advanced 1.4%, led by gains in technology stocks.