Shares of coronavirus vaccine developer Novavax, Inc. (NVAX) were moving sharply to the downside on above-average volume Monday.

The move comes despite the company announcing that it has added an additional arm in its ongoing Phase 3 COVID-19 vaccine study to evaluate the safety and efficacy of the vaccine in adolescents ages 12-17. 

The sell-off could be driven by the lack of an update from the company on the outcome of the late-stage study of its vaccine candidate NVX-CoV2373 that's underway in the U.S. and Mexico.

Novavax released in early March final data from the U.K. leg of the trial that confirmed 96% efficacy against the original strain. After a delayed start of the Phase 3 study in the U.S. and Mexico in late December, the company announced completion of enrollment on Feb. 22.

Apart from licensing deals and initiation of rolling reviews in the U.S., Europe, U.K. and Canada, the company has not announced any update on the late-stage study in the U.S. and Mexico, which may be needed for the FDA to make a call on the vaccine candidate.

With three vaccines already approved for emergency use in the U.S. and a few more outside of the U.S., a potential delay in the rollout of Novavax' vaccine candidate puts the company at a disadvantage. This poses a threat to the valuation of the shares, which looks now stretched.

A further update may be forthcoming when the company releases its first-quarter earnings report May 10.

CEO Gregory Glenn is scheduled to present at the 21st annual World Vaccine Congress taking place online this week.

NVAX Price Action

Novavax shares lost 17.65% Monday, closing at $195.12.