Steven Joffe of the Perelman School of Medicine commented on the unknown efficacy of a single dose of the COVID-19 vaccine, which was designed to be given in two doses. “Those unknowns are why some people say, ‘We should stick with what we know. By all means, do the trials to test [varied regimens], but don’t just wing it.’ Others say, ‘We are in a race against the virus.’ I’m not going to come down on one side or the other,” he said.