Pfizer announced Monday morning that its vaccine candidate is showing 90 percent efficacy in phase three trials, calling it a “historic moment.” The company believes it could get emergency FDA authorization before the month is up.
"Wow, it’s really encouraging. 90 percent efficacy is not what anyone was thinking about,” said UCSF epidemiologist Dr. George Rutherford. “We were hoping to get something in the upper numbers, but 90 is really spectacular success.”
The data is not final as the trial will continue until 164 people out of the 44,000 participants develop COVID-19, so the numbers could still shift. But Dr. Rutherford says scientists were expecting the vaccines to have efficacy closer to 55 percent, which is about on par with most flu vaccines.
“This is a real home run, if they can keep it up,” he said. “We want to continue to follow this, obviously, very closely. Pfizer’s really first out of the box with this kind of efficacy which I don’t think many people expected.”
He believes that phase three might not end for another few weeks. Pfizer plans to file for emergency use authorization as soon as the trial officially ends and submit the data to peer-reviewed journals.
“Efficacy is pretty close to being proven,” said Rutherford. “But you need to accumulate more and more experience about adverse events; if they occur, and if so how frequently do they occur and what are they.”
It is also not clear at this point how long the vaccine can protect people from infection.
Pfizer says it could produce 50 million doses this year and 1.3 billion next year.