A coronavirus vaccine developed by Pfizer is more than 90 percent effective, according to the first look at data from a late-stage U.S. trial involving nearly 44,000 participants.
An analysis of 94 trial participants who contracted Covid-19 showed that the vaccine was 94 percent effective, the company and its partner BioNTech said in a press release Monday.
The pair added that they expect to apply to the FDA for an emergency-use authorization before the end of the month, after they have collected sufficient data on the vaccine’s safety.
The better-than-expected result is the first Phase III data from any of the four candidates now in the final stage of testing in the U.S.
"I can’t imagine better news on the vaccine front," said Walid Gellad, director for the Center for Pharmaceutical Policy and Prescribing at the University of Pittsburgh. "Not only is it highly effective based on the press release, but there were 90 cases so we don’t have to deal with the skeptics about interim analyses, and there appeared to be no safety signals."
Others noted that the information Pfizer had released was promising but still incomplete. "We should remain a little cautious, said Michael Head, a senior research fellow in global health at the University of Southampton in the U.K. "The provisional findings are made available in a press release, and the study is ongoing."
President Donald Trump, who pushed unsuccessfully for a vaccine by Election Day, cheered the Pfizer result. "STOCK MARKET UP BIG, VACCINE COMING SOON. REPORT 90% EFFECTIVE. SUCH GREAT NEWS!" he wrote on Twitter.
President-elect Joe Biden issued a statement congratulating "the brilliant women and men who helped produce this breakthrough," but he cautioned that "the end of the battle against COVID-19 is still months away."
Even if a shot is authorized by late November, it will take many months before vaccination is widespread, Biden noted. "Americans will have to rely on masking, distancing, contact tracing, hand washing, and other measures to keep themselves safe well into next year," he said.
More on the math: The data and safety monitoring board overseeing the Pfizer trial was able to calculate the vaccine’s effectiveness by comparing the number of Covid-19 cases among people who received the vaccine to those who got a placebo.
The higher the number of cases among the placebo group versus the experimental group, the more effective the vaccine. Pfizer has not released the breakdown of the initial 94 cases, but its trial blueprint said that 26 cases among the placebo group and 6 among the experimental group would indicate that the vaccine was 77 percent effective.
The initial data exceeded those expectations.
But: Pfizer is still collecting safety data to prove to the FDA that the vaccine is safe as well as effective. The agency wants vaccine developers to follow at least half of trial participants for two months after their final dose of vaccine or placebo, and track any side effects.
Pfizer initially launched its trial with the goal of enrolling 30,000 participants before later expanding it to 44,000. The company will submit safety data on 15,000 people.
Supply and logistics challenges: Pfizer said Monday that it can make 50 million doses by the end of the year — enough to vaccinate 25 million people — and 1.3 billion by the end of 2021.
The U.S. government has already placed an initial order for 100 million doses of the vaccine at a cost of $1.95 billion and has an option to acquire another 500 million if the vaccine proves successful in Phase III trials.
Pfizer will aim to deliver those 100 million doses to the U.S. by March, said Alejandro Cané, the company’s U.S. medical and vaccine chief. But the company has not determined when and how it would distribute doses to other countries. Pfizer has signed deals with the U.K, Canada and Japan and is in talks with the European Union.
The vaccine could be tricky to distribute if it secures emergency-use authorization. It must be stored at -94 degrees Fahrenheit, which requires special freezers or dry ice. The shot can only withstand normal refrigeration for up to 24 hours and room temperature for no more than two hours after thawing.
Pfizer said last week that it would forego the government’s vaccine distribution system because of those ultra-cold transport and storage challenges. Instead it has developed a fleet of temperature-controlled shippers it has developed that use dry use to keep the vaccine at the correct temperature.
Background: The Pfizer vaccine relies a still-unproven technology involving genetic material known as messenger RNA, or mRNA.
When that mRNA is injected into the body, it prompts cells to make copies of the coronavirus’ spike protein — which in turn gets the immune system churning out antibodies.
The Pfizer shot is given as two injections weeks apart.
What’s next: Pfizer expects to seek emergency-use authorization from the FDA by the end of the month.
Zachary Brennan and Sarah Owermohle contributed to this report.