Shares of Novavax (NVAX) tumbled 5.85% in pre-market trading on Thursday, following news that the U.S. Food and Drug Administration (FDA) has missed a crucial deadline regarding the company's COVID-19 vaccine.

According to reports, the FDA failed to make a key decision concerning Novavax's COVID-19 vaccine within the expected timeframe. This delay comes just days after the FDA's vaccine chief was unexpectedly removed from their position, adding another layer of uncertainty to the situation.

The missed deadline and the recent shake-up in FDA leadership have raised concerns among investors about potential delays or complications in the approval process for Novavax's vaccine. For pharmaceutical companies like Novavax, regulatory decisions can have a significant impact on their market value and future prospects, especially for products as critical as COVID-19 vaccines in the current global health landscape.