The Food and Drug Administration will no longer approve COVID-19 vaccines for healthy people under 65 without rigorous trials.

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.

The FDA has approved Nuvaxovid to prevent COVID-19 in adults 65 years and older and high-risk individuals 12 through 64 years.