U.S. stock index futures indicated a muted start on Monday as markets reopen after the Christmas holidays and investors assess the spread of the omicron Covid-19 variant.

Dow Jones futures pointed to a lower open by around 10 points on Monday, while S&P and Nasdaq futures both indicated a slightly higher open.

On Thursday, with markets closed Friday, the Dow Jones Industrial Average added 196.67 points, or 0.55%, to 35,950.56. The S&P 500 rose 0.62% to 4,725.79 and closed at a record. The 500-stock average sits less than 0.4% from its intraday record high. The Nasdaq Composite gained 0.85% to 15,653.37.

Helping boost sentiment were new studies suggesting that omicron has a lower risk of hospitalization than other Covid variants.

U.S. infectious disease expert Dr. Anthony Fauci said Sunday that cases of Covid-19 are likely going to keep surging as the omicron variant rapidly spreads across the globe. 

“Every day it goes up and up. The last weekly average was about 150,000 and it likely will go much higher,” Fauci said on ABC’s “This Week.”

The U.S. has reported more than 52 million total cases, according to Johns Hopkins University. Driving the surge is the omicron variant, which took over as the dominant strain earlier this month.

A slew of economic data on Thursday last week showed a stable economy with improving labor and spending trends, but inflation at high levels. The Federal Reserve’s closely watched core personal consumption expenditures index rose 0.6% in November from the month prior. Core PCE rose 4.7% year-over-year in November, higher than the 4.5% rate expected.

On the data front Monday, a Dallas Fed manufacturing index is due out at 10:30 a.m. ET.

—CNBC’s Jessica Bursztynsky and Maggie Fitzgerald contributed to this article.