What a difference a few months make. Vaccine specialist Novavax (NVAX -2.24%) started the year poorly, continuing with the issues it has encountered since mid-2021.

Those headwinds included the difficulties it faced in launching its COVID vaccine in the U.S. and the significant slowdown in demand for these products, leading to a decline in revenue and earnings for the biotech.

However, several developments have jolted Novavax's stock since January. The company's shares are up by just under 200% this year. Can it keep up that momentum through the next 12 months? Let's find out.

A lucrative partnership with a larger biotech

Novavax faced significant uncertainty entering the year, but a recent partnership with Sanofi (SNY 0.62%), a much larger biotech, helped dispel some of this uncertainty. Sanofi made an up-front payment of $500 million to Novavax. 

In exchange, the France-based biotech obtained the right to commercialize Nuvaxovid, Novavax's COVID vaccine, in most countries worldwide. Sanofi also got the license to use the biotech's adjuvant technology to boost vaccine efficacy.

Novavax will be entitled to development and regulatory milestones of up to $700 million related to vaccines that use its adjuvant technology, in addition to potential royalties. Lastly, Sanofi acquired a 4.9% stake in the company for $70 million.

The market liked this deal since it will help improve Novavax's finances. The company expected revenue between $800 million and $1 billion from its COVID vaccine this year. It may or may not reach that total -- this market is hard to predict. But the $500 million investment from Sanofi by itself allows it to get more than halfway to the midpoint of its previous guidance in one fell swoop.

Novavax now expects revenue between $970 million and $1.2 billion for the year. The biotech is also working to reduce expenses significantly, a project it started last year and that has thus far been successful.

Elsewhere, Novavax is developing a combined COVID/flu vaccine and a stand-alone flu vaccine, which it expects will enter phase 3 studies sometime in the second half of the year.

These programs could produce final results within 12 months of today if Novavax runs pivotal trials in peak flu season in the fall and winter.

Is Novavax's stock worth buying?

Novavax has lost momentum since it first announced its new deal with Sanofi, but that's to be expected. Some shareholders were bound to take profits after its shares soared.

Even beyond that, it's unclear whether the vaccine maker can keep things up through the next year. First, its revenue will still largely depend on the performance of Nuvaxovid. While the injection of Sanofi's $500 million helped this year, that won't be a factor next year.

Although Novavax expects development milestones from Sanofi's investigational vaccines that use its adjuvant technology, it will likely take a while for many of these to materialize, and that's assuming these candidates perform well in clinical trials. Novavax won't collect the $700 million in milestones by this time next year, nor will it get much in royalties from Sanofi for newly developed vaccines that use its efficacy-boosting technology.

Novavax's combination COVID/flu vaccine is a promising candidate, but there are plenty of competitors here, some of which are ahead of the company. Ditto for the company's stand-alone flu vaccine. Ultimately, safety and efficacy will be the most important determinants of where each candidate ends up (although a first-mover advantage matters, too), but there is no guarantee that its investigational vaccines will pass muster in their upcoming pivotal studies.

Even after the stock recently soared on business developments, positive results from the biotech's upcoming late-stage studies could be major catalysts that send the stock price even higher. But negative results will have the opposite effect.

So it's difficult to know how the company will perform through this time in 2025. More importantly, Novavax's prospects still look somewhat risky and uncertain in my view: A lot would have to go right for it to become a winner over the long run.

That might change depending on how its pipeline programs evolve. But for now, there are much better biotech stocks to consider buying.