Novavax shares jumped more than 15% on Monday after the company secured a long-awaited U.S. regulatory approval for its COVID-19 vaccine, albeit with new conditions, which helped allay some investor concerns over the future of the shot.

Novavax had expected full approval for broader use by April 1, after the FDA reviewed data from a 30,000-person clinical trial showing the vaccine was safe and effective. But instead of a broad approval, the FDA asked the company to conduct more research.

Novavax Inc. jumped after US regulators fully approved its Covid vaccine, easing investors’ concerns after the clearance was delayed and US Health and Human Services Secretary Robert F. Kennedy Jr. raised doubts about its efficacy.