Moderna (NASDAQ: MRNA) delivered one piece of bad news to investors a few months ago: Chief medical officer (CMO) Tal Zaks will depart in September. The news came during the initial rollout of Moderna's very first product: its coronavirus vaccine. Zaks has been with the company for six years, and shepherded the vaccine from early-stage development through authorization. So, Moderna was about to lose a key character in its coronavirus vaccine story.