Pfizer said Monday that an early peek at the data on its coronavirus vaccine suggests the shots may be a
surprisingly robust 90% effective at preventing COVID-19, putting the company on track to apply later
this month for emergency-use approval from the Food and Drug Administration.
The announcement, less than a week after a presidential election that was seen as a referendum on
President Donald Trump’s handling of the crisis, was a rare and major piece of encouraging news lately
in the battle against the scourge that has killed more than 1.2 million people worldwide, including
almost a quarter-million in the United States alone. Confirmed cases in the U.S. were expected to
eclipse 10 million on Monday, the highest in the world.
"We’re in a position potentially to be able to offer some hope," Dr. Bill Gruber, Pfizer’s
senior vice president of clinical development, told The Associated Press. "We’re very
encouraged."
Dr. Anthony Fauci, the government’s top-infectious disease expert, said the results suggesting 90%
effectiveness are "just extraordinary," adding: "Not very many people expected it would
be as high as that."
"It’s going to have a major impact on everything we do with respect to COVID," Fauci said.
Pharmaceutical companies and various countries are in a global race to develop a vaccine against the
virus. Fauci said that the Pfizer vaccine and virtually all others in testing target the spike protein
the coronavirus uses to infect cells, so the results validate that approach.
Monday’s announcement doesn’t mean for certain that a vaccine is imminent: This interim analysis, from an
independent data monitoring board, looked at 94 infections recorded so far in a study that has enrolled
nearly 44,000 people in the U.S. and five other countries. Some participants got the vaccine, while
others got dummy shots.
Pfizer Inc. did not provide any more details about those infections and cautioned that the initial
protection rate might change by the time the study ends. Even revealing such early data is highly
unusual.
Whenever any vaccine arrives, initial supplies will be scarce and rationed, with priority likely to be
given to health care workers and others on the front lines. Pfizer has estimated that 50 million doses
of its vaccine could be available globally by the end of the year, which could cover 25 million people,
since it is given in two doses.
"We need to see the data, but this is extremely promising," said Dr. Jesse Goodman of
Georgetown University, former chief of the FDA’s vaccine division. He ticked off many questions still to
be answered, including how long the vaccine’s effects last and whether it protects older people as well
as younger ones.
Marylyn Addo, head of the tropical medicine unit at UKE hospital in Hamburg, Germany, said the interim
results were "an interesting first signal," but questions remain.
Global markets, already buoyed by the victory of President-elect Joe Biden, exploded on the news from
Pfizer. Major markets in Europe, where infections have soared, were up 5%. In the U.S., the S%P 500
surged 3.7% after the opening bell, and the Dow Jones Industrial Average was up more than 1,300 points.

Trump, who had suggested during the presidential campaign that a vaccine could be ready by Election Day,
tweeted on Monday: "STOCK MARKET UP BIG, VACCINE COMING SOON. REPORT 90% EFFECTIVE. SUCH GREAT
NEWS!"
The timing is likely to feed unsubstantiated suspicions from Trump supporters that the pharmaceutical
industry was withholding the news until after the election. Donald Trump Jr. tweeted: "The timing
of this is pretty amazing. Nothing nefarious about the timing of this at all right?"
Pfizer Chairman and CEO Albert Bourla said on CNBC that the election was always an artificial deadline
and that the data was going to be ready when it was ready. The independent data monitors met on Sunday,
analyzing the COVID-19 test results so far and notifying Pfizer.
"I am very happy," Bourla said, "but at the same time, sometimes I have tears in my eyes
when I realize that this is the end of nine months, day-and-night work of so many people and how many
people, billions, invested hopes on this."
He added: "I never thought it would be 90%."
Earlier this year, Fauci said he would be happy with a COVID-19 vaccine that was 60% effective.
Scientists have warned for months that any COVID-19 shot may be only as good as flu vaccines, which are
about 50% effective and require yearly shots.
Pfizer opted not to join the Trump administration’s Operation Warp Speed, which helped a half-dozen
drugmakers accelerate their vaccine testing and helped fund the work. Instead, Pfizer funded all its
testing and manufacturing costs itself. The company said it has invested billions of dollars.
The coronavirus shots, made by Pfizer and its German partner BioNTech, are among 10 possible vaccine
candidates in late-stage testing around the world — four of them so far in huge studies in the U.S.
Another U.S. company, Moderna Inc., also has said it hopes to be able to file an application with the
FDA later this month.
Volunteers in the final-stage studies, and the researchers, don’t know who received the real vaccine or a
dummy shot. But a week after their second required dose, Pfizer’s study began counting the number who
developed COVID-19 symptoms and were confirmed to have the coronavirus.
Because the study hasn’t ended, Gruber couldn’t say how many in each group had infections. But the math
suggests that almost all the infections counted so far had to have occurred in people who got the dummy
shots.
Pfizer doesn’t plan to stop its study until it records 164 infections among all the volunteers, a number
that the FDA has agreed is enough to tell how well the vaccine is working. The agency has made clear
that any vaccine must be at least 50% effective.
No participant so far has become severely ill, Gruber said. Nor could he provide a breakdown of how many
of the infections had occurred in older people, who are at highest risk from COVID-19.
Participants were tested only if they developed symptoms, leaving unanswered whether vaccinated people
could get infected but show no symptoms and unknowingly spread the virus.
FDA has told companies they must track half their participants for side effects for at least two months,
the time period when problems typically crop up. Pfizer expects to reach that milestone later this
month, but said Monday no serious safety concerns have been reported.
Because the pandemic is still raging, manufacturers hope to seek permission from governments around the
world for emergency use of their vaccines while additional testing continues — allowing them to get to
market faster than normal but raising concerns about how much scientists will know about the shots.
The FDA’s scientific advisers last month said they worry that allowing emergency use of a COVID-19
vaccine could damage confidence in the shots and make it harder to ever find out how well they really
work. Those advisers said it’s critical these massive studies are allowed to run to completion.
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AP writers Marilynn Marchione, Frank Jordans and Charles Sheehan contributed to this report.
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The Associated Press Health and Science Department receives support from the Howard Hughes Medical
Institute’s Department of Science Education. The AP is solely responsible for all content.