Pfizer's Covid vaccine candidate prevents 90% of infections in large study

The Covid-19 vaccine being developed by Pfizer Inc. and BioNTech SE prevented more than 90% of infections in a study of tens of thousands of volunteers, the most encouraging scientific advance so far in the battle against the coronavirus.

Eight months into the worst pandemic in a century, the preliminary results pave the way for the companies to seek an emergency-use authorization from regulators if further research shows the shot is also safe.

The findings are based on an interim analysis conducted after 94 participants contracted Covid-19. The trial will continue until 164 cases have occurred. If the data hold up and a key safety readout Pfizer expects in about a week also looks good, it could mean that the world has a vital new tool to control a pandemic that has killed more than 1.2 million people worldwide.

“This is about the best the news could possibly be for the world and for the United States and for public health,” said William Gruber, Pfizer senior vice president for vaccine clinical research and development. It was better than even the best result he had hoped for, he said.

With effectiveness for the first vaccines previously expected to be in the range of 60% to 70%, “more than 90% is extraordinary,” BioNTech Chief Executive Officer Ugur Sahin said.

‘Victory of Science’

“It shows that Covid-19 can be controlled,” Sahin said in an interview. “At the end of the day, it’s really a victory of science.”

The data do have limits. For now, few details on the vaccine’s efficacy are available. It isn’t known how well the shot works in key subgroups, such as the elderly. Those analyses haven’t been conducted. And it isn’t known whether the vaccine prevents severe disease, as none of the participants who got Covid-19 in this round of analysis had severe cases, Gruber said.

However, the strong reading from the first large-scale trial to post efficacy results bodes well for other experimental vaccines, in particular one being developed by Moderna Inc. that uses similar technology. Its big trial could generate efficacy and safety results in weeks. If that study succeeds as well, there could be two vaccines available in the U.S. by around year-end.

Pfizer expects to get two months of safety follow-up data, a key metric required by U.S. regulators before an emergency authorization is granted, in the third week in November. If those findings raise no problems, Pfizer could apply for an authorization in the U.S. this month. A rolling review began in Europe last month, and Sahin said regulators there are working with BioNTech to “further accelerate the process.”

So far, the trial’s data monitoring committee has identified no serious safety concerns, Pfizer and BioNTech said.

Leading the Race

The positive preliminary data mean the U.S. pharma giant and its German partner are on track to be first with a vaccine, after signing advance deals with governments worldwide for hundreds of thousands of doses. The companies have said they should be able to produce 1.3 billion doses -- enough to vaccinate 650 million people -- by the end of 2021. Only 50 million doses are expected to be available in 2020.

The shot relies on messenger RNA technology never before used in an approved medicine. Using mRNA, which essentially teaches the body’s cells to become vaccine factories, allowed it to be developed much faster than a traditional vaccine.

Pfizer had originally planned to conduct a first analysis of trial data after just 32 virus cases had occurred in the trial, which has enrolled 43,538 volunteers in multiple countries. Analyzing the data that early proved controversial among medical experts. Other companies working on vaccines planned to wait longer before scrutinizing trial information.

After discussion with U.S. regulators, Pfizer and BioNTech said they recently elected to drop the 32-case analysis and conduct the first analysis at a minimum of 62 cases, one of several changes made in the trial-analysis plan.

While Pfizer conducted those negotiations, it paused testing of participant samples for the virus, said Gruber. By the time Pfizer had made the changes in the trial plan and restarted virus testing a few days ago, some 94 cases had occurred, far more than the trial needed to meet the new threshold.

Pfizer raced to verify the data, which were still blinded to almost everyone at the company beside a few statisticians. Early on Sunday afternoon, an independent data monitoring committee that included a noted statistician and four infectious-disease experts met in a closed video session to review the results for the first time. Afterward, the panel brought Gruber, Sahin and other company representatives onto the call and told them the vaccine had easily achieved its efficacy goal.

“Everyone is pretty ecstatic,” said Gruber. He said that further details on the case breakdown weren’t available.

Uncertain Duration

The vaccine is being tested in a two-dose regimen. The trial started in July, and since most participants only received their second dose much more recently, nobody knows how long any protection will last.

Pfizer has found itself drawn into a contentious political debate about how quickly regulators in the U.S. should allow a vaccine to be given to Americans. President Donald Trump pushed to have a shot approved before Election Day, but regulators put in place rigorous standards that largely pushed that goal out of reach.

On Oct. 16, Pfizer Chief Executive Officer Albert Bourla said the companies could seek an emergency use authorization from U.S. regulators by late November if the trial results were to show the shot is safe and effective. Writing in an open letter, Bourla quelled fears that Pfizer might be racing the clock to bring out a vaccine before the presidential election.

Moderna is considered the next closest vaccine frontrunner. It has said it could get safety and efficacy data from its late-stage trial this month. Johnson & Johnson, which has a one-shot vaccine using a different technology, could get efficacy data from a final stage trial by the end of this year. AstraZeneca Plc is also working on a vaccine using different technology, with results from studies in the U.K. and Brazil expected by year-end.