I don't think he was worried about his base dying - he wanted to claim credit for Operation Warpspeed (the expedited development and rollout of the vaccines), with the usual "They said it would take 5 years, 10 years / it couldn't be done, but Trump did it in one!!!!" routine. He "deserves" some credit for doing a good thing (but certainly not the lion's share that he wants to claim, as usual).