Since the start of the coronavirus vaccine race, Moderna (MRNA -3.44%) and Pfizer (PFE 0.93%) have shared the spotlight. They've also run neck and neck every step of the way: through clinical trials, product authorization and rollout, and even winning government contracts.

Clinical trial data and real-world data have shown that on a safety and efficacy level, the two vaccine makers are about on par too. But recently, research pointed to one area where Moderna stands ahead of its bigger rival. Does that mean the Moderna vaccine is better than Pfizer's? Not necessarily. Let's take a look at the research -- and why Pfizer investors shouldn't worry about it.

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A study of healthcare workers

In a study, Moderna's vaccine produced more antibodies than Pfizer's vaccine, according to a research letter published in The Journal of the American Medical Association. In fact, Moderna's vaccine produced about double the number that Pfizer's produced. The study included 1,647 healthcare workers in Belgium. Of those, 688 had received the Moderna vaccine. And 959 had received the Pfizer regimen. The research showed higher antibody levels for the Moderna group in people who previously had been infected with COVID-19 and in those who hadn't been previously infected.

Antibodies have drawn a lot of attention since vaccine makers began clinical trials. That's because the goal of the vaccines is to stimulate the body to produce antibodies against the coronavirus.

After a first glance at the research letter, a Pfizer investor might worry. Higher antibody levels should lead to better protection, right? And if Moderna's vaccine beats Pfizer's, it may take major market share from its rival.

But wait. Let's not draw any hasty conclusions. Of course, the fact that Moderna's vaccine produces a high level of antibodies is positive for the company. But it doesn't necessarily translate into a better vaccine.

Here's why: The research referred to antibodies in general. It didn't specifically compare neutralizing antibodies. The most important type of antibody in this case is the neutralizing antibody. That's because it's known to block infection. Without specific information on neutralizing antibodies, it's impossible to say that one vaccine offers better protection than the other. Research published in May in Nature Medicine found that neutralizing antibody levels are "highly predictive" of coronavirus protection.

There may be a simple explanation for the higher levels of antibodies following a Moderna vaccine. Moderna's vaccine includes a heftier dose of mRNA -- 100 micrograms versus the 30 micrograms in the Pfizer vaccine. The timing of administration may also play a role in antibody production. Moderna's two doses are given four weeks apart versus three weeks apart for Pfizer's. The greater lapse of time may give Moderna an edge.

What does this mean for investors?

Pfizer investors shouldn't worry. And Moderna investors shouldn't cheer. The research as it stands doesn't link these levels of antibodies to protection. So far, the Pfizer and Moderna vaccines are on par when it comes to performance.

Both companies showed protection of more than 90% six months after the second vaccine dose in clinical trials. And both companies have said immunity will wane. That's why they're hoping to launch booster programs this fall. They've both submitted candidates to the U.S. Food and Drug Administration for authorization.

Pfizer and Moderna are expecting $33.5 billion and $20 billion, respectively, in vaccine revenue this year. (Pfizer shares vaccine profit with partner BioNTech.) It's too early to say how long vaccine revenue will stay at those levels or higher. But experts predict the coronavirus is here to stay. So, blockbuster revenue levels are likely to last.

All of this means there's reason to be optimistic about both vaccines -- and the future revenue prospects of both vaccine makers.