The head of the U.S. government's effort to develop a vaccine against COVID-19 reportedly said on Sunday that the first Americans could receive a vaccine as early as the second week of December, if all things go according to plan.

Moncef Slaoui, the head of the U.S.' "Operation Warp Speed" vaccine program, told CNN that the plan is to be able to ship vaccines to immunization sites within 24 hours of approval, expecting that the first people will be immunized across the U.S. on December 11 or 12.

On Friday, Pfizer submitted an application to the U.S. Food and Drug Administration for emergency use authorization for its COVID-19 vaccine candidate, and an FDA vaccine advisory committee is slated to meet December 10.

Slaoui said if authorized, the vaccine could be rolled out the next day. 

He also said that with the level of efficacy that has been shown in both Pfizer and Moderna's vaccines, 70 percent of the population being immunized would allow for true herd immunity to take place. This could likely happen somewhere in May.