What happened

On yet more worrying news about the omicron variant of the coronavirus, the fortunes of coronavirus stocks were mixed on Tuesday. Some of the ones doing particularly well in midafternoon trading were Novavax (NASDAQ:NVAX), up nearly 7%, and bellwether Pfizer (NYSE:PFE) with a 2.4% gain.

In contrast the co-developer of Pfizer's jab, BioNTech (NASDAQ:BNTX), was down by almost 3%. 

So what

It's interesting that the fortunes of partners Pfizer and BioNTech, which together developed the Comirnaty vaccine, were diverging so sharply.

While it seems that omicron had spread further, and earlier, than at first believed, it's still unknown how much of a threat it poses. This uncertainty is reflected in the contrasting development of the two stocks' share prices Tuesday.

Gloved hand filling a syringe from a vial.

Image source: Getty Images.

Also, over the past few days investors had pushed BioNTech higher. Now they might be either profit-taking or selling out on concerns that (unlike the sprawling Pfizer) their company's fortunes remain firmly tied to Comirnaty. If omicron ends up being less of a threat than feared, demand for either the current or a modified version of the shot shouldn't rise.

As for Novavax, since its NVX-CoV2373 vaccine isn't yet approved for use in any major jurisdiction in this hemisphere, it remains an underdog coronavirus stock. Investors pessimistic about omicron could see NVX-CoV2373 as a new go-to jab, next to Comirnaty and Moderna's mRNA-1273.

Novavax has filed for Emergency Use Authorization in a number of countries throughout the world, and those authorizations could be sped up by healthcare regulators if omicron becomes a serious threat.

Now what

It very much bears repeating that there are still far more questions than answers about omicron. So investors in Pfizer, BioNTech, Novavax, and any other coronavirus stock should proceed cautiously and not make rash investment decisions. We should know more very soon about this new variant.

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.