Watch CNBC's full interview with Pfizer CEO Albert Bourla

Albert Bourla, chairman and CEO of Pfizer, joins "Squawk on the Street" to discuss the company's trials of a Covid-19 vaccine and when he expects to see it ready for FDA approval. Right now, we do expect—we have a very good chance of having a conclusive efficacy of phase 3 before the end of October, he says. You need to see a statistically significant difference between between the control arm that are getting the placebo and the vaccinated arm, adds Bourla.