What happened

Shares of Dynavax (NASDAQ:DVAX) were skyrocketing 30.2% higher as of 3:47 p.m. EDT on Monday. The biotech didn't report any new developments today. However, the huge gain likely stemmed from last week's momentum, which was the result of positive comments from Dynavax's partner, Sinovac, as well as insider buying by Dynavax's interim chairman of the board, Andrew Hack.  

So what

Investors need to be cautious about putting too much focus on the comments last week made by Sinovac researcher Luo Baishan. When asked about the prospects for the COVID-19 vaccine being developed by Sinovac using Dynavax's CpG 1018 adjuvant, Baishan replied that he was 99% sure that the vaccine would be successful. However, Helen Yang, senior director of investor relations at Sinovac, was more measured in her reply to a similar question, stating: "It's very hard to say, very difficult to say at the moment. There are uncertainties, but the data: so far, so good."

$1 bill folded into an arrow pointing up

Image source: Getty Images.

It's definitely encouraging, though, that a key insider at Dynavax made a big bet on the company's future. Andrew Hack bought $5 million worth of shares last week. This brings Hack's total ownership to more than 8.5 million shares -- around 7.8% of Dynavax's total outstanding shares. 

Now what

The main thing to watch with Dynavax right now is the progress of the experimental COVID-19 vaccines being developed by various drugmakers using its CpG 1018 adjuvant. In addition, the company expects to report final immunogenicity data from its study of Heplisav-B in patients on hemodialysis in the second half of this year.

Meanwhile, don't be surprised if the biotech stock remains highly volatile. That's to be expected when there's a high short percentage of float, as is the case with Dynavax.

This article represents the opinion of the writer, who may disagree with the “official” recommendation position of a Motley Fool premium advisory service. We’re motley! Questioning an investing thesis -- even one of our own -- helps us all think critically about investing and make decisions that help us become smarter, happier, and richer.