The US can emerge from the depths of the COVID-19 crisis in the coming months if the federal government leads and executes an effective vaccination campaign (and if, as appears to be the case, emerging SARS-CoV-2 variants do not fully evade vaccine-induced immunity).
The limiting factors on the pace of population protection are the manufacturing capacity of the approved vaccines’ sponsors, the efficiency of administering available supply, and Americans’ willingness to take the shots.
A system dynamics model of vaccine inventory and daily vaccinations is useful for estimating when important objectives might be met.
Under a base case scenario, the US could reach a target of 75 percent of the population protected by the end of July, assuming three million shots per day can be sustained over several months and vaccine hesitancy recedes.
The expected arrival of another approved vaccine (from Johnson & Johnson) and the possibility of a slower, or more rapid, pace of daily vaccinations would alter the outlook in different ways.