Johnson & Johnson plans to start testing its coronavirus vaccine candidate in humans in July.
The company said it will move up the timeline by about two months to start clinical trials.
Previously the aim was to enter the clinic with the vaccine in September.
The study will start in the second half of July and enroll 1,045 healthy volunteers in the US and Belgium.
If the vaccine works, Johnson & Johnson has already pledged to distribute it at a nonprofit rate to help end the pandemic.
