- Moderna's experimental coronavirus vaccine looks likely to soon secure an emergency authorization from the Food and Drug Administration after a review by scientists at the agency turned up no unexpected red flags in clinical trial results submitted by the company.
- In a 54-page analysis released Tuesday, agency staff concluded Moderna's vaccine is both safe and "highly effective" at preventing COVID-19 in adults, including those who are older or at higher risk of severe disease. Vaccination was consistently protective across racial and ethnic groups, the FDA said.
- The FDA documents were made public ahead of a planned advisory committee meeting on Thursday, the final step in a review process that is expected to clear Moderna's vaccine for emergency use. On Monday, the first U.S. residents were given a shot developed by Pfizer and BioNTech that the FDA authorized last week.
Much like a review of Pfizer and BioNTech's vaccine last week, the FDA's analysis of Moderna's shot is similarly positive.
Results from a large trial testing the biotech's vaccine in some 30,400 people showed two shots, spaced 28 days apart, were about 94% effective in preventing COVID-19, a finding affirmed by FDA scientists. The agency's review was based primarily on an interim analysis of Moderna's trial, which was based on 95 cases of COVID-19. Five were in vaccinated volunteers, while 90 occurred in participants who had received placebo.
Since that analysis, Moderna's trial has reached its primary conclusion, after a total of 196 cases of COVID-19 were reported. While the FDA's scientists included those results in their review, they have not yet independently verified the complete data, a consquence of the speed at which the agency is reviewing the vaccine.
But the data are largely consistent, showing nearly idential rates of protection across all trial participants and similar effectiveness in older adults as well as younger. The final results, however, do indicate a slightly lower vaccine efficacy of 86% among volunteers aged 65 and older, although the difference may be the result of the smaller number of COVID-19 cases reported. At the early, interim analysis, protection was 100% among participants 65 years and older.
So far, data from both Moderna's and Pfizer and BioNTech's trials show the two vaccines can prevent symptomatic coronavirus disease, yet don't prove protection against asymptomatic infection.
Included in the documents made public Tuesday, however, is an addendum from Moderna that contains one of the first hints vaccination might also prevent infections that don't lead to the tell-tale COVID-19 symptoms. In Moderna's trial, volunteers were tested for coronavirus before both their first dose and their second.
Among the participants who tested negative at baseline, 14 who had been given their first vaccine dose tested positive prior to their second, compared to 38 who received placebo. The data suggest "some asymptomatic infections start to be prevented after the first dose," Moderna said.
In the FDA's review, however, agency scientists cautioned more data are needed to support any conclusion about protection from asymptomatic disease.
The documents also contain a hint of possible benefit following only one dose of Moderna's vaccine, rather than two. An analysis by FDA staff of nearly 1,000 study participants who had received just one dose found efficacy was about 80%. Measuring from two week after that one dose, efficacy was 92%, the FDA calculated.
Follow-up is extremely limited, however, at only a median of 28 days, and the sample size is small, limiting the conclusions that can be reached. Still, the FDA notes, "there appears to be some protection against COVID-19 disease following one dose."
Supplies of Moderna's shot, if it's authorized by the FDA, are expected to be very limited, a fact that's drawn debate about whether a one dose regimen should be more formally studied.
Importantly, the FDA reviewers found no unexpected side effects to vaccination and noted the rate of serious adverse events was low, at about 1% of participants, in both the vaccine group and the placebo group.
The shot, particularly after the second dose, did cause a range of symptoms like fatigue, headache, muscle pain and chills in most participants. In all but a small proportion, those side effects were mild to moderate in nature.
FDA scientists did note three cases of Bell's palsy, a type of facial paralysis, in participants who received the vaccine, compared to one among those given placebo. Four cases were observed in Pfizer and BioNTech's trial, although in both cases the FDA concluded there was insufficient evidence to determine a causal link.
General lymphadenopathy, or swelling of lymph nodes, was observed in 173 vaccinated volunteers, compared to 95 who received placebo, the FDA said.
Moderna is seeking an emergency authorization of its vaccine in adults older than 18, a cutoff slightly higher than Pfizer and BioNTech, which sought and received clearance in people aged 16 and older.
The same advisory committee will discuss Moderna's application in a daylong meeting Thursday, soon after which the FDA is expected to make a decision on granting emergency use authorization.
This story has been updated to clarify cases of Bell's palsy in the placebo group.