But what does that mean for us? Dr. Sharon Nachman, head of the Division of Pediatric Infectious Diseases at Stony Brook Children's Hospital, answers your questions.
Is this the potential breakthrough we have been waiting for?
What does the 90% effectiveness mean?
What about the overall safety, and how long would immunity last?
What about the diversity background of the participants?
Pfizer CEO on vaccine dosages, and Dr. Nachman:
How many people were in the trial, and what are the side effects?