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.

Pedestrians walk past Pfizer world headquarters in New York on Monday. Pfizer says an early look at its vaccine data suggests its shots may be 90% effective at preventing COVID-19. Associated Press/Bebeto Matthews

The announcement, less than a week after an election that was seen as a referendum on President 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.

“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.

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 2020, which could cover 25 million people, since it is given in two doses.

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.

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.

Public Citizen, the consumer advocacy group, called the release of the preliminary and incomplete data “bad science” and said that any enthusiasm for the results “must be tempered” until they are reviewed by the FDA and its independent experts.

“Crucial information absent from the companies’ announcement is any evidence that the vaccine prevents serious COVID-19 cases or reduces hospitalizations and deaths due to the disease,” the organization said.

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.

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. Those advisers said it’s critical these massive studies are allowed to run to completion.