Phase 3 of Pfizer's trial involved 43,538 participants. They received two doses of either the immunisation or a placebo, with 90% protected from the virus within 28 days of having their jabs.
Only 94 people who took part in the trial developed coronavirus and no serious safety concerns were reported, the US pharmaceutical firm said on Monday.
"Today is a great day for science and humanity. The first set of results from our Phase 3 COVID-19 vaccine trial provides the initial evidence of our vaccine's ability to prevent COVID-19," said Pfizer chairman and chief executive Dr Albert Bourla.
"With today's news, we are a significant step closer to providing people around the world with a much-needed breakthrough to help bring an end to this global health crisis.
"While we are all in the midst of a second wave and many of us in lockdown, we appreciate even more how important this milestone is on our path towards ending this pandemic and for all of us to regain a sense of normality," he added.