Leading infectious disease expert Anthony Fauci said on Monday that the progression from sequencing the coronavirus to getting Moderna`s potential vaccine into its phase three trial "is the best we, in the United States, have ever done."

The first injection for Moderna`s vaccine in partnership with the National Institutes of Health happened at 6:45 a.m. on Monday in Savannah, Georgia. The trial aims to enroll about 30,000 people from 89 widely dispersed sites across the U.S. over the next couple of months.

It is the first possible coronavirus vaccine to enter a phase three trial in the U.S. Phase one typically looks at a small number of people to see if the vaccine is safe. Phase two looks at an expanded group of people again to access safety and to see if the vaccine works. In the final phase three, the vaccine is tested in thousands of people to determine efficacy before seeking regulatory approval.

If the vaccine remains on track, Moderna previously said it will be able to deliver "approximately 500 million doses per year, and possibly up to 1 billion doses per year" starting in 2021.