Here are the most important news, trends and analysis that investors need to start their trading day:

• Wall Street under pressure on concerns about new Covid strain
• Doctors say vaccines still likely effective on new variants
• $900 billion compromise stimulus package set for votes
• Second vaccine cleared for emergency use in U.S. begins shipping
• Biden to get vaccinated to show Americans it's safe

1. Wall Street under pressure on concerns about new Covid strain

The Dow Jones Industrial Average was tracking for a 300 point decline at Monday's open as airlines, cruise lines and hotel stocks were getting slammed on concerns about a highly contagious new strain of coronavirus in the U.K., which triggered more severe lockdowns and travel restrictions across Europe. While losses in Dow futures were cut in half from their early morning lows, enthusiasm over Sunday's long-awaited new stimulus deal on Capitol Hill and the start of shipments of Moderna's vaccine were not enough to turn the tide on Wall Street. Even shares of red hot Tesla dropped 4% ahead of the electric auto maker officially joining the S&P 500 at Monday's open. Bitcoin wasn't able to hold on to gains after topping $24,000 for the first time ever overnight. The Dow, S&P 500 and Nasdaq dropped Friday from record highs, but they all turned in gains for the week.

2. Doctors say vaccines still likely effective on new variants

As the U.K. government holds a crisis meeting Monday to talk about the fallout from international travel bans, experts said it appears the existing vaccines will be effective in fighting off infection from new strains of the coronavirus. Dr. Scott Gottlieb told CNBC on Monday that existing Covid-19 vaccines will likely provide protection against the new coronavirus strain circulating in the U.K. "There is a strong belief here that the vaccine ... will have effectiveness in warding off infection from this new strain in England, in addition to the old strain that we've been contending with for months now," Vin Gupta, an affiliate assistant professor from the University of Washington's Institute for Health Metrics and Evaluation, told CNBC earlier Monday. Dr. Vivek Murthy, selected by President-elect Joe Biden to be surgeon general, made similar comments Sunday on NBC's "Meet the Press."

3. $900 billion compromise stimulus package set for votes

Lawmakers plan to vote Monday on a combined $900 billion compromise Covid-19 relief package and a $1.4 trillion plan to fund the government through September. The coronavirus aid deal, which saw fits and starts for months and months in Washington, includes a $300 per week federal boost to state unemployment benefits, a $600 direct payment to most Americans, along with a new round of subsidies for hard-hit businesses and money for schools, health providers and renters facing eviction. In a statement, Biden said the $900 billion plan "provides critical temporary support," but he added that it's "just the beginning." In the new year, Democrats are expected to push for aid for state and local governments. That was left out of the current bill, in a compromise with Republicans who shelved their desire for liability protections for businesses.

4. Second vaccine cleared for emergency use in U.S. begins shipping

Moderna this weekend began distributing its Covid vaccine, the second approved for emergency use by the FDA, with trucks going to more than 3,700 locations across the U.S. The rollout of the vaccine from Pfizer and BioNTech, the one first cleared in the U.S., began last week as health-care workers and residents and staff at nursing homes started to get the initial shots. The CDC's Advisory Committee on Immunization Practices on Sunday recommended that 30 million frontline workers — including first responders, teachers, postal workers and grocery store workers — get next priority. In all, that move would make 51 million people eligible to get inoculated in the next round, though the timetable was unclear.

5. Biden to get vaccinated to show Americans it's safe

Biden plans to get his first dose of coronavirus vaccine on live television Monday. The president-elect has defended his decision, recently saying, "I don't want to get ahead of the line, but I want to make sure we demonstrate to the American people that it is safe to take." Vice President Mike Pence, House Speaker Nancy Pelosi, D-Calif., Senate Majority Leader Mitch McConnell, R-Ky., and other lawmakers were given shots Friday. Vice President-elect Kamala Harris is expected to receive her first shot next week. It's not clear when outgoing President Donald Trump, who recovered from Covid-19 this fall, would be vaccinated. The White House has said he's still discussing timing with his doctors.

— Reuters and The Associated Press contributed to this report. Follow all the developments on Wall Street in real time with CNBC Pro's live markets blog. Get the latest on the pandemic with our coronavirus blog.