The U.K. trial will end when either 116 people develop symptoms of Covid-19, or when 63 people develop moderate to severe Covid-19. At that point, the researchers will “unblind” the results and compare how many of the infections were in the vaccinated group compared with the placebo group.
The trial’s goal is that the vaccine will be at least 60 percent more effective than a placebo.
The company also said it would soon publish its trial design, known as a protocol, following the lead of several other vaccine makers that did so after independent researchers called for more transparency.
Dr. Gregory M. Glenn, Novavax’s president for research and development, said in an interview on Thursday that the company was running a smaller safety trial in South Africa, in addition to the larger Phase 3 trials in the United Kingdom and the United States.
“There are so many things that are uncertain, we need to try to have three shots on goal,” he said. “So that the F.D.A., or anybody, could look at any one of these trials and say, you know, that’s evidence the vaccine is working.”
The company’s U.S. trial will be conducted in collaboration with the National Institutes of Health, and Dr. Glenn said that trial was expected to include 30,000 people and to begin in the middle of October. Johnson & Johnson announced this week that it was beginning a 60,000-person trial of its coronavirus vaccine.
Novavax’s U.K. trial will distinguish itself from competitors because up to 400 of the volunteers will also receive an approved flu shot. This kind of study can be valuable for doctors by determining whether it is safe to give patients two vaccines at the same time.
Dr. Heath said one possibility was that Covid-19 would surge every winter along with the flu. “A scenario where both vaccines can be given at the same time, and thereby minimize disease over the busy winter months, you know, is a good one to push for,” he said.