Pfizer and BioNTech are moving to expand Phase 3 of their Covid-19 vaccine by 50%, which could allow companies to collect more safety and efficacy data and increase the diversity of study participants.
The companies said in a press release that they would increase the size of the survey to 44,000 participants, compared to the initial goal of recruiting 30,000 people.
The US Food and Drug Administration will have to approve the change before it takes effect.
“Companies continue to expect the final efficiency reading to be likely by the end of October,” the statement said. The Pfizer and BioNTech study is likely to be among the first in the United States to report efficacy data from a phase 3 trial.
The expansion of the study is likely to make it easier for the company to demonstrate whether the vaccine is effective against SARS-CoV-2, the virus that causes Covid-1
The companies said the trial is expected to reach its initial target of 30,000 patients next week. Moderna, which began its trial on the same day as Pfizer, said on September 4 that it was working to increase the diversity of trial participants in its study, “even if these efforts affect the speed of recording.”
The Pfizer / BioNTech study may end earlier than Moderna’s, although both start on the same day and for different reasons. Both vaccines require a second shot; Pfizer is given after three weeks, while Moderna is given after four. The Pfizer trial also began counting Covid-19 cases earlier after participants received their photos than the Moderna study.
But the Pfizer / BioNTech vaccine may also be one of the most difficult of experimental vaccines to spread if they prove effective. The vaccine should be stored at -70 degrees Celsius.
There was political pressure to move the vaccine quickly, with President Trump saying it could be available before election day. Last week, several drug manufacturers, including Pfizer, pledged not to move the vaccine sooner than was justified by the results of their clinical trials.