President Donald Trump’s administration is slated to lay out its approach to Covid vaccination at an event Tuesday that could spell major changes in what is required to get regulatory approval for immunizations.

Novavax originally showed its vaccine was safe and effective in a 30,000-person clinical trial. The FDA had been on track to grant Novavax full approval – without restrictions -- by its April 1 target date, according to two people with direct knowledge of the situation who spoke on condition of anonymity to discuss confidential agency matters.

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.