When we think of halting the coronavirus pandemic, we think of vaccination. And when we think of who to vaccinate, we think of adults. Older adults, in particular, have been most vulnerable to the coronavirus. The U.S. Food and Drug Administration has authorized three vaccines -- those from Pfizer (NYSE:PFE), Moderna (NASDAQ:MRNA), and Johnson & Johnson. And the U.S. has fully vaccinated 21% of the adult population so far.