Sure, there's plenty of shorts that will cover after a one day 20% drop but shorts aren't NVAX's problem.
It's the lack of buyers.
Until earnings call we won't know if company is going to maintain, raise, or decrease guidance.
Secondly, the advantage NVAX had over PFE and MRNA is gone now that the government is ordering the new variant vaccines for the fall.
We have no visibility into the availability of the current NVAX vaccine for Americans and no timeline for NVAX new variant approval and availability.
So the approval was a nothingburger, IMO. It finally opens the door to all those good possibilities for NVAX but there's no timeline which is neccessary to support the stock price and bring in new buyers.