Novavax (NVAX) shares plummeted 5.06% in Tuesday's trading session, despite the company announcing the completion of its U.S. marketing authorization transfer for its COVID-19 vaccine, Nuvaxovid, to Sanofi. This transfer triggers a $25 million milestone payment to Novavax, following a similar transfer in the EU last month.

The stock's decline comes as a surprise given the positive news of the milestone payment. However, investors may be interpreting the transfer of marketing rights as a sign that Novavax is relinquishing control over a key product in its portfolio. The company stated that it anticipates receiving the milestone payment in the first quarter of 2026, which may also be contributing to the market's lukewarm response.

Adding to the downward pressure, TD Cowen maintained its Hold rating on Novavax stock. This cautious stance from analysts, combined with the mixed signals from the Sanofi deal, appears to have led investors to reassess their positions in Novavax, resulting in the significant stock price drop during the trading session.