Others will begin in August, September and October, the US government's top infectious diseases expert have said.
The news comes as Moderna Inc, which is at the forefront of the country's vaccine development efforts, reiterated earlier in the day that a late-stage trial with 30,000 volunteers would begin this month.
"We may be able to at least know whether we are dealing with a safe and effective vaccine by the early winter, late winter, [or] beginning of 2021," Dr Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, said in an interview to JAMA Network.
Earlier today, Dr Francis Collins, the director of the US National Institutes of Health, said the Trump administration's vaccine-acceleration program could generate a safe and effective COVID-19 vaccine by year-end.
