The race is on to develop a vaccine to fight off COVID-19. Biotech company Moderna says they're on track to finish enrollment for a Phase-3 study of its vaccine by the end of September. Dr. Anthony Fauci, the nation's top infectious disease expert, says he remains "cautiously optimistic" in regards to the vaccine. He spoke with KTLA with more information about its development, when it can be expected, who will receive it, and more.