Trump has encouraged people to get vaccinated before. But never as part of a sustained public campaign. All it would take is a little flattery to enlist him and he could boast about the vaccines as part of his own legacy, possibly getting holdouts among his own voters to take the shots.
This would be distasteful for the Biden administration, especially after the events of Jan. 6. Indeed, Trump could have more profitably spent the months he has devoted to re-litigating the presidential election taking a vaccine victory lap instead. Just this week, Trump has mused about the chairman of the Joint Chiefs of Staff being an unsuitable partner for a coup and dropped such statesmanlike quotes as, "Many say I am the greatest star-maker of all time. But some of the stars I produced are actually made of garbage."
But Trump's continued relevance is beyond the current administration's control. If President Biden believes what he says about promoting national unity and turning the page on a divisive predecessor's inflammatory approach to politics, he will enlist that predecessor in the national COVID-19 initiative. Biden does not have to let Trump talk about bleach, but he can amplify the 45th president's role in the vaccines' creation and approval.