On March 19, 2020, as Covid-19 swept across the world, I challenged everyone at Pfizer to “make the impossible possible”: to develop a vaccine more quickly than anyone ever had before, ideally within six months and certainly before the end of the year. Uğur Şahin, the CEO of our partner BioNTech—a German company focused on cancer immunotherapies—did the same with his team.

A version of this article appeared in the May–June 2021 issue of Harvard Business Review.