Pfizer says early data signals COVID-19 vaccine may be 90% effective; but it doesn’t mean a vaccine is imminent

Pfizer said Monday that an early peek at the data on its coronavirus vaccine suggests the shots may be a 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 U.S. alone.

Pharmaceutical companies and various countries are in a global race to develop a vaccine against the virus.

“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.”

Monday's announcement doesn't mean 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.

Authorities have stressed it's unlikely any vaccine will arrive much before the end of the year, and initial supplies will be rationed.

“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.

If Pfizer's vaccine ultimately pans out, "it’s going to be a while before this has a major impact at the population level,” Goodman said.

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., Dow futures also rose 5% and were up about 1,400 points just over two hours before the opening bell.

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!”

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, Dr. Anthony Fauci, the government’s top infectious-disease expert, 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.

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 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.