The change is made possible by the fact that Covid-19 is so prevalent across the country, according to a person familiar with the matter. The more virus there is in the United States, the more likely it is that participants will be exposed to it, which means researchers can draw conclusions based on a smaller trial.
Changing the size of the study does not indicate that the results will come on a different timeline, or anything as to whether they will be positive or negative.
During a press briefing on Wednesday, Moncef Slaoui, the head of Operation Warp Speed, briefly mentioned the change.
“We have already recruited over 38,000 subjects into the study,” Slaoui said. “With J&J, we have decided to limit recruitment to around 40,000 subjects, which will take place by the end of this week, so in the next two [or] three days. “
In a statement, J&J said, “We continue to anticipate that provisional data from the ENSEMBLE trial will be available by the end of January. If the vaccine is safe and effective, an emergency use authorization application could be submitted to the FDA in February. “
The J&J study, launched on September 23, was the largest Phase 3 trial of a Covid-19 vaccine. The vaccine that J&J developed uses an adenoviral vector, a type of genetically engineered virus that causes the body to produce a protein to which the immune system then responds, theoretically inoculating the recipient against the virus.
Like other Covid-19 trials, the goal is to follow volunteers enrolled in the study until 154 of them have contracted the virus that causes the disease. In the case of the J&J study, to be counted, a case of Covid-19 must be severe or moderate and occur at least two weeks after vaccination.
As Covid-19 cases skyrocket in the United States, J&J will reach this milestone while recruiting fewer patients. This leaves the J&J study roughly the same size as the one conducted by Pfizer and BioNTech, which included 44,000 volunteers in their study of the first vaccine to deliver positive results, and a little larger than the 30,000 patient study conducted. by Moderna, who developed the second vaccine to show positive results.
Johnson & Johnson is also conducting a second study using two doses of the same vaccine in Europe and the United States. This study plans to recruit 30,000 volunteers.
Lev Facher contributed reporting.