J&J's study will test the vaccine against a placebo and assess the shot's safety and immune response in 1,045 healthy people aged 18 to 55 years, as well as those 65 years and older.
The trial will take place in the United States and Belgium.
US biotech Moderna Inc is at the forefront of Covid-19 vaccine development and has started testing its candidate in a mid-stage trial that will enroll 600 patients.
The company expects to begin late-stage trials in July.
AstraZeneca, Sanofi, Pfizer
are all at various stages of development of their vaccine candidates.
There are currently about 10 coronavirus
vaccines being tested in humans and experts have predicted that a safe and effective vaccine could take 12 to 18 months from the start of development.