I'm fully expecting the first shots to be in arms early next week. If administration can closely follow distribution, this could mean an additional 20,000,000 Americans getting vaccinated just in March. I keep getting conflicting information on how many Americans are over 18, but from what I can tell I believe that would be somewhere between eight and nine percent of American adults getting vaccinated from just Johnson and Johnson.
I still think that the super majority of Americans who get vaccinated will be taking mRNA vaccines, but I think Johnson and Johnson and other one dose regiments will be the most widely employed vaccines in the developing world. Logistically it's just much simpler.