President Donald Trump has said that a vaccine might be ready by the end of the year. The Centers for Disease Control and Prevention has notified health departments to be ready to distribute a vaccine by late October or early November. Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, has said that if data from clinical trials is overwhelmingly positive, trials could be cut short.

Adams did not clear up the confusion during his appearance on Good Morning America, calling the chances that a vaccine is ready early "possible, but not probable."

"We want to make sure states are available to distribute it," Adams said. The CDC guidance to health departments to be ready to distribute a vaccine in November is a "just in case" scenario, Adams explained.

On the off chance that a vaccine is ready by early November, having systems in place to distribute it would ensure that the vaccine gets to people who need it most, he added.