Vaccine maker Novavax (NASDAQ:NVAX) saw its shares jump 18% on June 5 and another 20% in pre-market trade this morning. NVAX stock is up over 300% year-to-date.Novavax also said it will be able to deliver an updated Covid-19 vaccine in September, made without the use of controversial mRNA technology.More important to investors may be the fact that over 36% of Novavax shares are now being held short, including over half traded off listed exchanges.NVAX stock is due to open today at $24.10 per share, a market ...