A Covid-19 vaccine being developed by Pfizer has been found to be more than 90% effective in preventing the virus, in a major study.
Pfizer, which developed the vaccine with the German drug maker BioNTech, released only sparse details from its clinical trial, based on the first formal review of the data by an outside panel of experts.
But the development is the most encouraging scientific advance so far in the battle against a pandemic that has killed more than 1.2 million people, and indicates that the company is on track to file an emergency use application with US regulators later this month.
The findings are based on an interim analysis conducted after 94 participants, split between those who got a placebo and those who were vaccinated.
The company said that the analysis found that the vaccine was more than 90 percent effective in preventing the disease among trial volunteers who had no evidence of prior coronavirus infection.
If the results hold up, that level of protection would put it on par with highly effective childhood vaccines for diseases such as measles. No serious safety concerns have been observed, according to the company.
Pfizer doesn’t plan to stop its study until it records 164 infections among all the volunteers, a number that the US Food and Drug Administration 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.
Company executives have said by the end of the year it will have manufactured enough doses to immunize 15 to 20 million people.
“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.”
Independent scientists have cautioned against hyping early results before long-term safety and efficacy data has been collected. Moreover, no one knows how long the vaccine’s protection might last.
The 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 US.
Another American company, Moderna Inc., also has said it hopes to be able to file an application with the FDA later this month.