Moderna's (MRNA -3.52%) last earnings report was chock-full of good surprises. The company announced its first-ever profit, which surpassed $1 billion, thanks to Moderna's single product: the coronavirus vaccine. The company expects more than $19 billion in vaccine sales this year and reported progress on vaccine orders for next year, too.

After all of that, what more could we possibly expect in Moderna's next earnings report? Well, Moderna likely will update its vaccine revenue expectations for the year, and investors will surely have an eye on the company's profit level.

Those elements are key. But the most important thing I'll be looking for in Moderna's earnings report next week has to do with a subject most of us have been talking about in recent weeks. And that is... drum roll, please...

Two people study something on a computer in a modern office.

Image source: Getty Images.

A subject that's garnered attention

I'll be eager to hear an update regarding Moderna's investigational booster shot. The subject of potential booster shots has garnered a lot of attention in recent days because of two factors. The first is the increase in variants -- most specifically, the highly contagious delta that's now dominant in the U.S. The second is the possibility of waning immunity in those vaccinated early on in the initial vaccine rollout.

For the moment, the U.S. Food and Drug Administration (FDA) and the Centers for Disease Control and Prevention (CDC) say boosters aren't needed for those who are fully vaccinated. But that could change quickly if current disease trends continue.

Also, both Moderna and rival Pfizer have said boosters may be needed about eight months after initial vaccination. In the U.S., vaccination rates peaked in early April. That means the period of October through January may be ideal for a booster. Of course, the variants could accelerate things, and that means an extra lift to immunity may be better sooner instead of later.

So what's Moderna's plan? Here's what we know so far: The company is investigating three possibilities for a booster shot: an extra dose of its authorized vaccine, a booster candidate targeting the beta variant (first identified in South Africa), and a combination of the authorized vaccine and the booster candidate.

Back in May, Moderna announced early positive phase 2 data regarding the first two candidates. The company also said it would provide data on the third candidate -- the combination -- when available.

Three details to watch for

During next-week's earnings report, I'm hoping for data from the third booster candidate. The idea of combining the already successful vaccine with a strain-specific formula sounds like a promising strategy.

I'll also be on the lookout for any decisions about which candidate Moderna may choose to move forward with toward authorization. And finally, I'll listen for a possible message regarding timeline.

Earlier this spring, CEO Stéphane Bancel said he hoped to have a booster ready by fall. Will this still be the plan? And if so, will Moderna offer us any details?

Pfizer said earlier in the month that it expects to ask for authorization of its booster in the coming weeks. The Pfizer booster is a third dose of its authorized vaccine.

If Moderna hopes to compete with Pfizer in the near term in the booster market, it can't fall behind. Of course, some may say that a person already vaccinated by Moderna will have to wait for a Moderna booster. Technically, yes. But studies have already been looking into the idea of combining vaccines. If the coronavirus situation worsens and Pfizer is the only company with an authorized booster, it's possible it could win major market share.

Boosters represent a lot when it comes to revenue. Moderna has fully vaccinated 63 million people in the U.S. If each of them gets a Moderna booster, that equals more than $960 million in sales.

I used the $15.25 price the U.S. originally paid for doses to calculate. (This doesn't mean an immediate $960 million order -- it just indicates that future orders may be this much bigger as the U.S. takes into account the total number of doses required for each American.) The number clearly will increase as more people get vaccinated -- and this doesn't even take into account international sales.

Moderna shares already have gained more than 200% this year. Any delays in the booster program could equal a pullback. But if this program with billion-dollar potential stays on track, the stock could head considerably higher now and into the future.