Moderna's extraordinary results were based on 95 coronavirus infections that occurred in trial participants receiving either the vaccines, mRNA-1273, or an inert placebo. Data showed that of those 95 cases, 90 occurred in participants that received the placebo, resulting in that estimated efficacy. The vaccine requires two doses, 28 days apart.
The biotech also demonstrated that the vaccine is generally well tolerated, with the majority of adverse events being mild or moderate in severity and mostly short-lived. Adverse side effects more often occurred after the second dose of the vaccine, and were typical of other common drug side effects like fatigue, headache, and injection site pain.
Since these are preliminary results, they may be subject to change as the study's participant pool continue to be monitored for infections. Moderna intends to submit for an emergency use authorization with the U.S. Food and Drug Administration (F.D.A.) in the next few weeks based on these interim results. The company also plans to submit applications to global regulatory agencies.
The two vaccines both employ experimental technology called messenger RNA (mRNA) which is synthetic genetic proteins that "train" an individual's immune system to create antibodies against the virus without using a dead or weakened form of the virus, which is a popular method in common vaccines like those made for the flu. This type of vaccine technology can be produced at scale more rapidly than conventional vaccine, though its has yet to be approved for use in vaccines or other drugs.
While both vaccines are very similar in design and administration, Moderna's may have logistical distribution advantage over Pfizer's due to the fact that Moderna's candidate can be stored at standard refrigerator temperatures for up to 30 days while Pfizer's must be kept at subzero temperatures. Pfizer's vaccine can only last at refrigerator temperatures for up to five days.
Pending F.D.A. approval for public use, the United States could have about 20 million doses of each vaccine by the end of December. Health and Human Services Secretary Alex Azar told CNBC's "Squawk Box" on Monday that the F.D.A. will move "as quickly as possible" to approve both drugs for emergency use.
"We hope those applications for both Pfizer and Moderna will get in as quickly as possible," Azar told CNBC. "We will independently call those balls and strikes on the data and evidence, but we're going to do so as quickly as possible, consistent with just making sure the science, the evidence and the law support authorization."