It's too early to say which company -- or companies -- will win the coronavirus vaccine race. But we do have tools to identify the most promising players. It's important to look at timelines, clinical trial data, and a company's ability to fund and manufacture billions of doses of a safe and effective vaccine. More of this information is available now than was the case a few months ago.

Considering these elements, Moderna (MRNA -0.74%) and Pfizer (PFE) would be on my buy list. The clinical-stage biotech and big pharma player are among the 11 programs currently in phase 3 trials. Both are working on messenger RNA (mRNA) vaccines. Unlike traditional vaccines, they don't introduce weakened virus into the body. Instead, they instruct the body to make specific disease antigens to fight future infection. Let's take a closer look at both companies to see exactly what makes them the best coronavirus bets right now.

Man in suit wearing gloves holding cash and vials

Image source: Getty Images.

1. Moderna is a longtime leader

Moderna has been a frontrunner in the vaccine race since the beginning. In March, the company became the first to launch an investigational coronavirus vaccine into human trials. Since then, others have caught up. But Moderna so far has scored a win in other areas too.

The biotech company recently reported a noteworthy component of its phase 1 data. In trial participants aged 56 through 70 and in those 71 and older, neutralizing antibody activity was two to three times higher than that seen in recovered coronavirus patients. Neutralizing antibodies are known to block infection. This performance in older adults is important because the elderly have been among the most vulnerable to the coronavirus. Moderna had announced similar results in younger trial participants earlier.

The company completed phase 2 trial enrollment in July. More than than 25,000 volunteers are enrolled in the phase 3 trial, nearing the company's goal of 30,000 participants. As of Sept. 16, 10,025 trial participants had received the complete treatment course, which consists of two doses. Moderna promised an update once phase 3 enrollment is complete. That should be soon, since the plan is to achieve full enrollment by the end of this month.

Funding and manufacturing capacity are two additional strengths. The U.S. government has awarded Moderna a total of $2.48 billion in support of the vaccine candidate. About $1.52 billion is for the manufacturing and delivery of 100 million doses. The Department of Health and Human Services (HHS) also granted the company $955 million to support development through approval. As for manufacturing, Moderna is scaling up to deliver 500 million to 1 billion doses annually beginning next year.

2. Pfizer joined forces with a biotech

Pfizer allied with German biotech BioNTech (BNTX -1.44%) in March in order to develop a coronavirus vaccine candidate. Its phase 1/2 trial launched in May. Like Moderna, in early trials, Pfizer's vaccine candidate produced neutralizing antibody levels higher than those of recovered coronavirus patients in younger and older adults.

The company has enrolled more than 29,000 participants in its phase 3 trial. It recently amended protocol to enroll as many as 44,000 in the trial. That's up from the original plan for 30,000 volunteers.

As for U.S. government funding, HHS and the Department of Defense (DoD) have offered Pfizer $1.95 billion for the supply of 100 million vaccine doses. Pfizer aims to deliver 1.3 billion doses globally next year if its candidate is approved.

Moderna and Pfizer seem about even in the race at this stage. But there is one detail that might set Pfizer apart. Pfizer says that it's on track to report a "conclusive readout on efficacy" by the end of next month. At the same time, U.S. Food and Drug Administration (FDA) Commissioner Stephen Hahn has said that the agency may consider data for an emergency use authorization (EUA) before companies have finished phase 3 trials. That means, if Pfizer believes next month's readout proves the safety and efficacy of its candidate, it could apply for an EUA straightaway.

While the situation looks promising for both Pfizer and Moderna, that doesn't mean one or both of them will win the coronavirus vaccine race. Anything can happen at any point of the clinical trials process. And a setback could be fatal for either program.

What's an investor to do?

It depends on investment style. If I didn't mind risk and wanted to bet on two of the strongest players in the race right now, I'd go for Pfizer and Moderna. If I wanted to minimize risk -- even if that meant minimizing my gains -- I would limit the size of my investment in Moderna, or avoid the stock entirely if I were truly risk averse.

Here's why: The coronavirus program has driven Moderna's 254% share increase this year. As a clinical-stage biotech company, the potential coronavirus vaccine is its only immediate revenue engine. If Moderna succeeds, the shares are sure to soar. But if Moderna's program fails, I would expect a big share decline.

Pfizer's shares are less dependent on coronavirus news. The big pharma company has 89 pipeline projects and a full portfolio of commercialized products. It isn't depending on the investigational coronavirus vaccine for revenue. So even if Pfizer is successful, the stock probably won't skyrocket upon a vaccine's EUA or general regulatory approval. But I would expect the program to contribute to Pfizer's earnings and share performance over time. And that's great news for long-term investors.