An experimental COVID-19 vaccine being developed by the National Institutes of Health and biotech company Moderna, Inc., might have results by November or sooner, the federal government’s top infectious disease scientist, Anthony Fauci, said Monday.

The public-private partnership to develop the vaccine moved into a crucial new stage Monday with the start of a Phase 3 clinical trial that aims to enroll 30,000 people around the United States.

Three more potential vaccines that are also part of the administration’s “Operation Warp Speed” effort also may soon enter the final phase of testing, according to NIH Director Francis Collins. Those vaccines are being developed by AstraZeneca, Johnson & Johnson, and Novavax, respectively. 

The fact that the number of coronavirus infections continues to rise in the U.S. could make it potentially easier to detect whether the vaccine is effective, which is why NIH leaders expressed optimism that research will yield results by year’s end. Fauci, director of the National Institute of Allergy and Infectious Disease, said the goal is for the vaccine to reduce the risk of coronavirus infection by 60 percent. 

Not everyone will be able to get the vaccine immediately. But Moderna chief executive Stéphane Bancel said if the vaccine proves safe and effective, and the Food and Drug Administration subsequently authorizes or approves it, the company would be able to produce 500 million doses and potentially up to a billion doses during its 2021 fiscal year, starting early next year. 

Collins said if the vaccine is approved later this year, initially tens of millions of doses will likely be available. Last week, a panel convened by the National Academy of Medicine began a process to develop recommendations to the federal government on who should receive the first doses of a vaccine — such as health care workers or other vulnerable populations — when a product is approved but still scarce.

Fauci said he was reluctant to predict the vaccine could be ready before November, but noted it was a “distinct possibility” if a high infection rate persists and study enrollment goals are met.

The unprecedented speed at which the vaccine is being developed has prompted concerns that the Trump administration may pressure the FDA to authorize or approve a product that isn’t safe or effective. But Collins, Fauci and Bancel repeatedly emphasized that they would not compromise safety or effectiveness. 

“Nothing is being done here to compromise the safety of this particular trial or others like it, nor will we compromise on an ultimate conclusion about whether the vaccine is effective,” Collins said in a call with reporters. “Those issues are going to be tested in the most rigorous way.” 

Earlier in July, researchers reported that the first phase of the trial, with 45 participants, found no serious adverse reactions to the vaccine but that more than half of the participants experienced symptoms like headache, fatigue, chills and pain where they were injected. Participants receive two shots, with the follow-up dose administered 28 days after the initial injection. The side effects were more common after the second dose.

While the earlier phases of testing focus on safety, the early analysis indicated that the vaccine produced an immune response that was stronger than that seen in people who were previously ill with COVID-19. 

The Phase 3 study that began Monday aims to enroll 30,000 people by the end of the summer, with half of the participants randomly given a placebo instead of the actual vaccine. The first participant was injected on Monday morning in Savannah, Georgia, and 89 testing sites are open throughout the U.S.

People interested in participating can take a survey to assess whether they are qualified to participate in this or other future clinical trials of potential coronavirus vaccines. 

Collins acknowledged the challenge of recruiting a diverse group of participants, particularly when some of the groups who experience the worst COVID-19 outcomes, like the Black and Latino communities, have been historically underrepresented in clinical research. He said the NIH is working to engage those communities to ensure the trial appropriately reflects the U.S. population. 

“We recognize that COVID-19 has put into sharp relief the health disparities that afflict populations in the United States,” he said. “If we wish to demonstrate the safety and efficacy of a vaccine to prevent that illness, we would particularly want to be sure that those groups are well represented in vaccine trial enrollment.”