Shares of Novavax (NVAX) plummeted 10.40% during Friday's trading session, following news that the U.S. Food and Drug Administration (FDA) has requested the company to complete a new clinical trial for its delayed Covid-19 vaccine.

According to a Wall Street Journal report, the FDA's demand for additional clinical data has dealt a significant blow to Novavax's hopes of bringing its Covid-19 shot to market in the near term. This setback comes at a crucial time for the biotechnology company, which has been working to develop its vaccine candidate amid fierce competition from other pharmaceutical giants.

The request for a new clinical trial suggests that the FDA may have concerns about the existing data or efficacy of Novavax's vaccine. This development is likely to cause further delays in the potential approval and distribution of the vaccine, which could explain the sharp negative reaction from investors. As the pandemic continues to evolve and vaccination efforts progress worldwide, any delays in bringing new vaccines to market could have significant implications for both public health and the company's financial prospects.