Moderna Inc.'s highly effective COVID-19 vaccine, in addition to protecting millions, is officially a cash cow.

The company disclosed during its earnings presentation Aug. 5 that it expects the shot to generate $20 billion in sales this year. Now it has to figure out what to do with its windfall as it tries to justify a market valuation that has surged by more than $100 billion since May. That's a nice problem to have. But it's also an urgent strategic issue.

The Cambridge, Massachusetts-based biotechnology firm’s astonishing stock surge has been driven by the success of its vaccine and excitement about its underlying messenger RNA technology, which it is also employing in other shots and treatments in early stages of development.