What happened

Shares of Moderna (NASDAQ:MRNA) soared 10.5% this week as of the market close on Thursday. Novavax (NASDAQ:NVAX) wasn't far behind with its stock up 10.2%. Shares of another COVID-19 vaccine maker, BioNTech (NASDAQ:BNTX), jumped 7%.

There were several reasons behind the solid gains for each of these biotech stocks. Moderna announced on Tuesday that the European Commission was buying another 150 million doses of its COVID-19 vaccine for delivery next year. BioNTech revealed that it was considering initiating a dividend next year. Novavax received a bump after a Canadian official announced the completion of a new manufacturing facility that will be used to produce the company's COVID-19 vaccine.

In addition, Moderna and BioNTech shareholders breathed a sigh of relief after the U.S. Food and Drug Administration (FDA) stated that it would add a warning to the label of messenger RNA (mRNA) COVID-19 vaccines related to a potential risk of heart-inflammation issues. The FDA decision isn't likely to impact the sales of the mRNA vaccines developed by Moderna or BioNTech and its partner, Pfizer.

COVID-19 vaccine vial with syringe on top of a stock chart.

Image source: Getty Images.

So what

It makes sense that Moderna enjoyed the biggest gain this week. The company's new European supply deal will significantly boost its revenue. The FDA decision to add a warning label to mRNA vaccines wasn't a surprise. The agency's action helped reassure some investors.

Novavax should also benefit in a tangible way from the completion of the Canadian Biologics Manufacturing Centre (BMC). The company is working closely with the National Research Council of Canada to transfer technology on manufacturing its NVX-CoV2373 COVID-19 vaccine at the BMC.

BioNTech's announcement about a potential dividend was arguably the least important news for these three vaccine makers. Chief Operating Officer and CFO Sierk Poetting stated that the biotech would "examine, in accordance with the legal and statutory provisions, whether and in what amount a resolution on the distribution of dividends should be proposed" to shareholders at the next annual general meeting. That's not exactly a firm commitment.

Now what

The key things to watch with Moderna and BioNTech now are how many additional supply deals the companies pick up for their COVID-19 vaccines. The emergence of the Delta coronavirus variant could play a big factor in the fortunes of both biotechs.

For Novavax, the next major catalyst to look for is the company's regulatory filings for approval of NVX-CoV2373 in the U.S., U.K., and Europe. Novavax expects to complete its regulatory submissions in the third quarter of this year. 

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.