Moderna (NASDAQ:MRNA) has enrolled the first participants in a phase 2 clinical trial testing mRNA-1273, its vaccine against the novel coronavirus that causes COVID-19.

The move puts the biotech one step closer to potentially having the first COVID-19 vaccine available in the U.S., although the timing isn't all that surprising. Moderna announced plans to start the mid-stage study in April, followed by an endorsement by the Food and Drug Administration last month. And phase 1 data for the vaccine released May 18 certainly looked promising enough to justify moving to mid-stage testing.

Hand holding a syringe and a person's shoulder

Image source: Getty Images.

Moderna plans to enroll 600 participants in the study, with half of them being 55 years of age or older. Based on the phase 1 study, Moderna plans to test two doses of the drug, which will be compared with a placebo. Each participant will receive an initial vaccination and a booster to increase antibody production.

The phase 2 clinical trial might be able to read out faster than the 45-participant phase 1 study that took about two months to gather data. That's because all participants can be dosed immediately, unlike in a phase 1 dose-escalation study where safety data from each dose has to be gathered before the next dose can be started. Of course, there are substantially more participants in the phase 2 study, but it shouldn't be too hard to find 600 people who are interested in enrolling in the study.

Moderna is shooting for starting the phase 3 clinical trial in July. The company is still working on the design of the study, but presumably it'll need to have thousands of participants to gather enough safety data to get the vaccine approved by regulators.

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