Moderna unveiled the details for how it’s running its late-stage COVID-19 vaccine trial.

Moderna CEO Stephane Bancel announced that the company will know if its vaccine works in November. His comment comes four days after the CEO of Pfizer said it expects to have conclusive info on its vaccine by the end of October. Moderna is one of three drugmakers backed by the U.S. in late-stage testing for a potential vaccine along with Pfizer and AstraZeneca. AstraZeneca’s late-stage trial is on hold in the U.S. after a patient became ill, though it has resumed in the UK. On September 8th, nine drug companies, including Moderna, released a letter pledging that they would prioritize safety and uphold ” the integrity of the scientific process” in their efforts to develop coronavirus vaccines.

Moderna also announced it was slowing enrollment slightly in its clinical trial to ensure it has sufficient representation of minorities most at risk for the disease. The company so far has enrolled 25,296 people in the trial and expects to enroll up to 30,000 participants. Their experimental vaccine contains genetic material called messenger RNA, or mRNA, which scientists hope provokes the immune system to fight the virus, CNBC reports.

“We’re very close to that vaccine as you know and I think much closer than I think most people want to say,” Trump said during a White House press briefing. “We think we can start some time in October. So as soon as it’s announced we’ll be able to start. That will be from mid-October on. It may be a little bit later than that.”