Stocks fell on Monday as Omicron variant concerns tarnished market sentiment. The Dow Jones Industrial Average dropped over 400 points, while the S&P 500 and Nasdaq fell over 1%. The S&P 500 has fallen over 3% in the past three sessions, while the Nasdaq has tumbled about 3.8%.

The World Health Organization on Saturday said that Omicron cases double in a matter of 1.5 to 3 days in areas with community transmission, renewing lockdown concerns as the United States heads into the winter season.

Here's how the market settled to start the week:

S&P 500 Index (SPY  ): -1.14% or -52.61 points to 4,568.03

Dow Jones Industrial Average (DIA  ): -1.23% or -433.28 points to 34,932.16

Nasdaq Composite Index (QQQ  ): -1.24% or -188.74 points to 14,980.94

Goldman Sachs lowers its GDP forecast on BBB uncertainty:

Goldman Sachs lowered its 2022 GDP growth forecast after Democratic Senator Joe Manchin on Sunday said that he would not support President Joe Biden's "Build Back Better" (BBB) plan, meaning the bill will not have enough votes to pass the Senate.

Goldman Sachs Chief Economist Jan Hatzius said in a note to clients on Sunday that the failure of the bill would slow economic growth in 2022.

"BBB enactment had already looked like a close call and in light of Manchin's comments we are adjusting our forecast to remove the assumption that BBB will become law. While BBB in its current form looks unlikely, there is still a good chance that Congress enacts a much smaller set of fiscal proposals dealing with manufacturing incentives and supply chain issues," the note said.

The firm slightly lowered its real GDP growth forecast for each of the first three quarters in 2022, now projecting 2% growth in the first quarter, followed by 3% and 2.75% in the following two periods. Goldman previously expected growth of 3%, 3.5% and 3%.

Oracle to buy Cerner in $28.3 billion deal:

Oracle (ORCL  ) announced Monday that it plans to buy the electronic medical records company Cerner Corp. (CERN  ) for $28.3 billion, making it the computer software company's largest deal ever.

The deal is expected to close next year, and could help Oracle boosts its presence in health care by giving the company access to Cerner's health data for its cloud services. Cerner shareholders will receive $95 in cash for each share held, which is a premium of nearly 6% compared to the stock's Friday close.

Here's how market benchmarks started trading soon after open:

S&P 500 Index: -1.33% or -61.45 points to 4,559.19

Dow Jones Industrial Average: -1.28% or -454.32 points to 34,911.12

Nasdaq Composite Index: -1.53% or -237.69 points to 14,942.55