It seems like a distant memory now, but Novavax (NVAX 1.67%) delivered a jaw-dropping 2,700% return in 2020. The stock was also a big winner throughout much of last year.

But then the bottom dropped out. Between late September 2021 and mid-June 2022, Novavax's share price plunged by more than 80%. However, the once high-flying stock has begun to rebound in a major way, soaring close to 70% in the last month. 

There's no doubt about it: Novavax is sizzling hot once again -- even with its small pullback on Monday. Is it time to buy the vaccine stock

Behind the hot streak

Most stocks have performed dismally over the past few weeks as the broader market indexes have fallen. Novavax has been able to swim against the current for a good reason. Actually, there are several good reasons behind the stock's recent hot streak.

On June 23, the Committee for Medicinal Products for Human Use (CHMP) of the European Medicines Agency (EMA) recommended expanded authorization for Novavax's COVID-19 vaccine Nuvaxovid in adolescents aged 12 to 17. Less than two weeks later, the European Commission authorized the vaccine for use in immunizing adolescents.

On July 7, the EMA approved SK bioscience as a manufacturer of Nuvaxovid for the European Union. This move gave Novavax two authorized suppliers for the European market. All the doses supplied to the EU previously were made by Novavax's partner, Serum Institute of India.

Not all of Novavax's good news came from Europe. On the same day CHMP recommended authorization of Nuvaxovid for adolescents, the vaccine received Emergency Use Authorization (EUA) in Taiwan.

Also, Novavax made a positive impression at the U.S. Food and Drug Administration (FDA) Advisory Committee review of data for boosters targeting the coronavirus omicron variant on June 28. One member of the advisory committee even said that Novavax's data looked "more impressive" than the data presented by Pfizer and Moderna

What could make the stock move even higher?

There are two key hurdles Novavax has left to jump through that could make the stock move even higher. The most important is for the company to win U.S. EUA for its COVID-19 vaccine.

The FDA's Advisory Committee has already unanimously recommended authorization. However, the agency must first complete a review of Novavax's manufacturing changes before it makes a decision.

This EUA would only be for Novavax's vaccine to be used in adults who had not already been vaccinated. Nearly 77% of Americans ages 18 and up have already been fully vaccinated. Many of those who haven't yet received a COVID-19 vaccine probably won't want Novavax's vaccine, assuming it wins EUA.

That leads us to the second hurdle for Novavax: winning authorization for booster doses. This EUA would open up a much bigger market opportunity for the company. And based on the positive feedback from the recent FDA advisory committee meeting, Novavax could have a pretty good shot (no pun intended) of securing authorization for booster doses after it receives EUA for its primary two-dose series.

Time to buy?

Despite its huge gain in recent weeks, Novavax stock only trades at 2.2 times expected earnings. This dirt cheap valuation shows that many investors are worried about the company's longer-term prospects. No one knows what the demand will be for COVID-19 vaccines over the next few years. 

Because of this uncertainty, Novavax isn't the kind of stock that risk-averse investors will find attractive. But what about more aggressive investors?

Novavax could have some solid catalysts on the way with potential FDA authorizations. Its long-term prospects might also be better than some think. Novavax is arguably in the lead in developing a combination COVID-flu vaccine. If COVID-19 becomes endemic, as many experts predict it will, this combo vaccine could generate strong recurring revenue for the company.

The potential risks for Novavax are real, but so are the potential rewards. I think it's a good time to buy Novavax stock -- at least for some investors.