Final Results from Moderna vaccine trial are stellar!

Moderna just announced the final efficacy results from its Phase 3 study for the SARS-CoV-2 vaccine are complete, and they are exceptionally promising.


Some highlights:

  • 30k participants were in the study, 15k given the vaccine, and 15k given placebo, which was randomized and double-blind, meaning neither participant or health care workers knew who received placebo or vaccine.

  • There were 196 total COVID-19 cases detected, in which participants reported symptoms and SARS-CoV-2 was confirmed by PCR test.

  • Out of these cases, 185 were in the placebo arm, and only 11 in the vaccine arm, for an efficacy of 94.1%, meaning that it is estimated that 174/185 of the infections that would have occurred in vaccinated participants were prevented by the vaccination.

  • Of these, 30 involved severe cases, all in the placebo arm, and none in the vaccine arm. This provides strong evidence that the vaccine prevents severe, not just mild, disease.

  • The reported safety profile is very good, with the only side effects being typical to vaccines, including temporary soreness at injection sites, some headaches, fatigue, etc. Ongoing continuous follow-up of participants will be done to confirm there are no serious side effects.

  • The study included a good number of individuals who were older, with pre-existing conditions, or minorities, including 42% either >65 or with co-morbidities including diabetes, severe obesity, or cardiac disease, and 37% from communities of color (Hispanic, Black, Asian, mixed race). Thus, this trial was not just sampling healthy, young, white individuals but a diverse group reasonably representative of the USA population.

A publication will be submitted for peer review shortly, and Moderna is applying for an emergency use authorization (EUA) from the FDA.


This study is so clean and well-designed, which makes these results all the more impressive and exciting, with the study:

  • Results being from single, well-designed trial.

  • Protocol being publicly available so all study details are clear and transparent.

  • Double-blinded and randomized

  • Placebo-controlled

  • Single dose of vaccine, pre-specified and used throughout

  • Well representative of age/race/co-morbidity dynamics in population

  • Including all participants in the analysis, i.e. not selecting certain subgroups for the analysis

  • Efficacy endpoint being well-defined and consistently applied.

My previous extremely critical commentary on the AstraZeneca results is because the studies upon which the recently released interim analysis results were based seem to have had none of these components, and thus the results are extremely hard to interpret at this point. Hopefully transparent sharing of the data and peer reviewed publication will clear up many of these questions. It is important for people not to conflate the questions raised in that analysis with the Moderna study, which does not have those same questions.


Of course, there are still questions about the Moderna vaccine that have to be addressed, but it seems based on what we know that it is reasonably safe and effective, and will be approved for emergency use by the FDA in the coming weeks. The remaining questions include:

  • Does it prevent asymptomatic disease? Since only those with symptoms were tested, the study can't rule out the possibility that more individuals were infected and infectious, but remained asymptomatic. But based on the extremely high efficacy for preventing infections with severe or mild symptoms, it is not unreasonable to expect it to prevent asymptomatic infections, as well.

  • How long does immunity last? Given isolated anecdotal evidence of reinfections, some are worried that immunity after infection might not last, and that also immunity from vaccines may not last. As I have detailed in other past blog posts, there is strong statistical evidence that these reinfections are exceptionally rare and results from numerous recent papers have suggested most infected and recovered individuals have durable immunity of at least 6 months, and a targeted vaccine is expected to produce at least as durable immunity as a natural infection.

  • How feasible is it to distribute? This mRNA vaccine requires freezer storage, but only requires -4 degrees Fahrenheit and can use existing freezer storage, so has far fewer distribution problems than the BioNTech/Pfizer that requires -92 degrees Fahrenheit storage.

This is exceptionally good news, and I expect to see this vaccine approved by EUA and distributed to HCW and possibly high risk groups later this month. The broad distribution of this and other vaccines has the potential to get the pandemic under control this Spring, and allow us to see the light at the end of the tunnel, with our lives returning to a greater sense of normalcy by Summer and Fall 2021.





1,837 views1 comment