The findings of a large U.S. trial have shown that the coronavirus vaccine developed by AstraZeneca and the University of Oxford is 79% effective in preventing symptomatic illness and 100% effective against severe disease and hospitalization. Ruud Dobber, president of AstraZeneca U.S., joined CNBC's Meg Tirrell and the CNBC's "Squawk Box" crew on Monday to discuss the results.