Novavax (NVAX) stock plummeted 5.07% in intraday trading on Tuesday, despite the company reporting positive results from a recent study. The sharp decline comes as the U.S. Centers for Disease Control and Prevention's (CDC) advisory panel begins a review of vaccine guidelines, raising uncertainty in the vaccine market.

The Shield-Utah study, results of which were released early Tuesday, showed that Novavax's COVID-19 vaccine induces lower reactogenicity symptoms compared to mRNA vaccines. Reactogenicity refers to the physical manifestation of the inflammatory response to vaccination, such as pain at the injection site or fever. While this finding could be seen as a positive for Novavax's vaccine, it failed to prevent the stock's significant drop.

Adding to the market's unease, the CDC's Advisory Committee on Immunization Practices (ACIP) began a two-day meeting to review guidelines for several vaccines, including recommendations for the next generation of COVID-19 shots. The panel is expected to discuss whether to narrow recommendations on who should receive updated COVID shots for the 2025-2026 season. This potential policy shift could have significant implications for vaccine manufacturers like Novavax, possibly contributing to the stock's decline as investors await the outcome of these discussions.