The U.S. has approved the world’s only twice-a-year shot to prevent HIV, maker Gilead Sciences announced Wednesday. It’s the first step in an anticipated global rollout that could protect millions – although it’s unclear how many in the U.S. and abroad will get access to the powerful new option.

While a vaccine to prevent HIV still is needed, some experts say the shot — a drug called lenacapvir — could be the next best thing. It nearly eliminated new infections in two groundbreaking studies of people at high risk, better than daily preventive pills they can forget to take.

“This really has the possibility of ending HIV transmission,” said Greg Millett, public policy director at amfAR, The Foundation for AIDS Research.