Stock prices of coronavirus vaccine developers have been soaring over the past few months, with businesses reporting early trial data, then moving into later-stage studies. Some investors have waited on the sidelines, hesitating about buying at the high.

The month of August may have brought an entry point from a price perspective for three seemingly unstoppable players. Moderna (MRNA -1.69%), up 385% this year through its peak in July, slipped about 5% in August. Inovio (INO -0.32%), which had surged 860% at its highest point in July, is down 35% in August. And Novavax (NVAX -5.11%) has lost 20% in August after increasing 36-fold from January through July.

A doctor's gloved hand injects someone's arm with syringe

Image source: Getty Images.

So what's behind the recent losses? Some early investors may have been locking in gains after an incredible run since the start of the year. Other, more short-term investors might be switching from one stock to another as they bet on which player will next announce positive news. The recent share declines aren't an automatic reason to stay away from these companies -- but on their own, they're also not a reason to buy. Let's take a closer look at these clinical-stage biotechs before making any decisions.

Moderna's high note

Moderna is finishing the month on a high note. Announcing its first trial results on older adults, management said its investigational vaccine led to neutralizing antibody production in all 20 participants. This echoes its earlier results in younger trial participants. Neutralizing antibodies are considered important, as their role is to block infection. Since the elderly have been among the most vulnerable to the coronavirus, any successful vaccine must properly address this group.

The latest results from Moderna's phase 1 trial are positive. But we'll need to see confirmation in a larger group, so stay tuned for results from the ongoing phase 2 and 3 trials. The company aims to enroll 30,000 participants in its phase 3 trial by September, and has already enrolled more than half that number since July 27.

Funding to bring the potential vaccine to market and manufacturing capacity are two other key points -- and there, too, Moderna is winning. The U.S. government has awarded Moderna as much as $2.48 billion in development support and vaccine orders. Moderna is scaling up to manufacture 500 million to 1 billion vaccine doses annually.

Novavax's big award

Novavax turned heads when Operation Warp Speed -- the government's initiative to help bring a vaccine to market by January -- offered it $1.6 billion in early July. At that point, it was the biggest Operation Warp Speed award yet. Novavax's total funding for the program now stands at about $2 billion.

At the time of the Operation Warp Speed award, Novavax was a step behind Moderna and some other players, as it hadn't yet reported clinical trial data. But in early August, Novavax reported positive phase 1 results, saying its vaccine candidate produced antibody activity in all participants. Novavax's report only concerns volunteers ages 18 through 59. Unlike Moderna, Novavax doesn't yet have data on older patients. Earlier this week, the company launched the phase 2 portion of its study; for this, it plans to enroll 1,500 participants, with about half of them in the 60-to-84 age range.

As for manufacturing, Novavax's acquisition of a facility in the Czech Republic puts it on track to produce about 1 billion doses as of next year. And manufacturing agreements with others mean capacity likely will be higher. Novavax has also agreed to supply the U.K. government with 60 million vaccine doses as early as the first quarter.

Inovio's trial results

Inovio, too, has reported positive phase 1 data. But investors were disappointed by a lack of detail regarding neutralizing antibodies. Moderna and Novavax said their vaccine candidates produced neutralizing antibody levels higher than those in recovered coronavirus patients. Inovio simply said all trial participants produced immune response based on neutralizing antibody and T-cell activity, which is not the same thing. The company aims to publish full data in a medical journal, which will allow easier comparison of Inovio's vaccine candidate performance with rivals'. Inovio plans to start a phase 2/3 trial in September. That will be another element to watch.

As for funding, Inovio comes in behind Moderna and Novavax. The company has garnered about $110 million so far to support its program. And it hasn't yet announced agreements to supply any countries with a vaccine if approved. Inovio is set to produce at least 100 million doses next year, also well behind its rivals.

Company Trial Stage 2021 Manufacturing Capacity Funding
Moderna Phase 3 500 million to 1 billion doses $2.48 billion
Novavax Phase 2 At least 1 billion doses $2 billion
Inovio Phase 2/3 to begin in September 100 million doses $110 million 

Buy none, one, or all three?

It depends on your risk tolerance. If you're not an aggressive investor, it's best to stay away from any clinical-stage biotech companies riding the coronavirus wave. Their share prices are too dependent on coronavirus news -- and they don't have commercialized drugs to generate revenue if their coronavirus vaccine programs fail.

If you are a biotech investor with an appetite for risk, though, now is a good moment to pick up shares of Moderna or Novavax. Moderna has reported the most data so far, and its vaccine candidate is further along in the trial process. I like Novavax for a different reason. Earlier this spring, the company reported excellent phase 3 data for its investigational flu vaccine, for which it plans to apply for regulatory approval. So, if you invest in Novavax, it's possible another revenue source is on the horizon.

As for Inovio, add it to your watch list and wait for more trial data. Though Inovio and others may not be the closest to the finish line, if they produce a strong vaccine, they may be winners in the long run.