• The pan-European Stoxx 600 index ended down 0.34%, with most sectors and major bourses in negative territory.
• The U.K.'s drug regulator approved Wednesday the Oxford-AstraZeneca coronavirus vaccine for use.
• U.K. lawmakers approved the post-Brexit trade deal Wednesday.

European stocks closed slightly lower on Wednesday after U.K. lawmakers approved a Brexit trade deal and investors reacted to further positive Covid vaccine developments.

The pan-European Stoxx 600 index ended down 0.34%, with most sectors and major bourses in negative territory.

London's FTSE 100 index was down 0.7% despite the coronavirus vaccine developed by the University of Oxford and AstraZeneca being authorized for emergency use in the U.K.

The announcement marks another step in the global battle against the pandemic and will allow the U.K. to greatly expand its Covid-19 immunization program started in December. So far, the Pfizer-BioNTech vaccine has been given to 600,000 people in the U.K., according to government statistics. Shares of AstraZeneca closed slightly lower on Wednesday.

European markets are bucking a lackluster trend seen in their global counterparts Wednesday; Stocks in Asia-Pacific were mixed in trade overnight after major indexes on Wall Street snapped their multi-day winning streaks on Tuesday. Meanwhile, the dollar weakened against other major currencies.

China's 2019 GDP growth was revised downward to 6.0%, according to a statement released Wednesday by the country's National Bureau of Statistics. That compared against a pre-revision 2019 growth rate of 6.1%.    

Meanwhile, U.S. stock index futures were slightly higher as the market tried to reclaim record highs. The major averages closed lower on Tuesday, giving up early gains that pushed stocks to record highs at the opening bell. Lawmakers in Washington continue to disagree over direct payments to Americans that are part of an economic stimulus package amid the ongoing coronavirus pandemic.

Senate Majority Leader Mitch McConnell blocked Senate Minority Leader Chuck Schumer's effort to fast-track the bill, passed by the House late Monday, that would increase checks to $2,000 from $600. Stimulus payments could go out as early as Tuesday evening, Treasury Secretary Steven Mnuchin said.

President Donald Trump has supported higher payments, and on Tuesday said in a tweet that the move should be approved "ASAP. $600 IS NOT ENOUGH!"

Lawmakers in the U.K. approved on Wednesday the post-Brexit trade deal reached by negotiators on Christmas Eve.

There are no major earnings or data releases Wednesday.

- CNBC's Eustance Huang and Pippa Stevens contributed to this market report.