Health care was the top issue for Americans voting in Tuesday's midterm elections.

Based on exit polls by NBC News, more U.S. voters cited it as their top concern on the ballot than any other issue — marking the first time in at least a decade that's happened.

Pascal Soriot, the CEO of European pharma giant AstraZeneca, believes that now the Democrats have won back control of the House of Representatives, they will "have to work collaboratively with the (President Donald Trump) administration.

"We will see what they come up with," he told CNBC's "Squawk Box Europe" on Thursday.

AstraZeneca is a biopharmaceutical company with a market capitalization of around $100 billion. It derives 31 percent of its product sales from the U.S.

"It is clear the (U.S.) market is under pressure, changes are coming. (It) is really hard to imagine what will happen to prices. But I think one of the things that I would say, as far as the U.S. marketplace goes, is it needs to gain transparency," Soriot said.

During the 2016 presidential campaign, Trump pledged his commitment to lowering prescription drug prices. In July 2018, the president tweeted that drugmakers "should be ashamed" for raising prices.