An interim analysis released today indicates that Moderna’s mRNA-based COVID-19 vaccine candidate is nearly 95% effective, making it the second candidate to show such a high-level of efficacy. Last week, Pfizer and BioNTech reported their mRNA vaccine candidate was more than 90% effective based on an interim analysis. These results have spurred optimism among public health officials who are struggling to control a surging pandemic, and have exceeded the expectations of many vaccine experts.

HVP Editor Kristen Jill Abboud discussed these latest results with Wayne Koff, founding President and CEO of the Human Vaccines Project (HVP). An edited version of the conversation appears below. This special issue also includes reactions from several experts in the field and a summary of Moderna’s ongoing Phase III efficacy trial, including trial demographics and their plans for submitting their vaccine for regulatory authorization.

Moderna reported that of the 95 COVID-19 cases in the trial so far, 90 were among placebo recipients and only five were among vaccine recipients, which corresponds to an efficacy of 94.5%. What is your initial response to this news?

The efficacy they are seeing is once again extraordinary. It is as promising of a result as anyone could have hoped for. These results are a reaffirmation of mRNA as a vaccine platform. It also affirms the targeting of the Spike (S) protein of the virus, which is what most of the vaccine candidates are based on. That said, we await data on the durability of the vaccine-induced responses. Based on what we know, however, this is very encouraging. Now, we eagerly await data being fully reported in a peer-reviewed publication because it is difficult to fully analyze the results until that happens.

Among the 95 COVID cases analyzed so far in both vaccine and placebo groups, 15 of the volunteers were over 65 years old and 20 volunteers were from what the press release refers to as “diverse communities.” The company also reports that the safety and efficacy profile is consistent across subgroups. Does this give you confidence that when the trial is complete, we will have a reasonable understanding of how the vaccine works in these populations?

This trial involves more than 30,000 participants and they have enrolled a lot of people over age 65 and in diverse communities, so I think we will get the data on the efficacy in these populations. This information is going to be really important, because as we’ve seen, individuals over the age of 65 and those in diverse racial/ethnic populations are more likely to die as a result of COVID-19. If there is a consistent level of safety and efficacy among these sub-populations, that would be really great news.

This mRNA vaccine seems to protect against cases of severe disease, but there isn’t yet any data on prevention of infection. Is there any vaccine platform in particular that stands out as being the most likely to protect against infection?

The initial data on severe disease is fabulous—all 11 cases of severe disease that have been observed so far have occurred among placebo recipients. This is preliminary and is based on a small number of severe cases, but this is still a really important observation. It’s hard to know which vaccines will work better at preventing infection because the vaccine platforms are quite different—mRNA, recombinant protein, viral vectors, and live and killed vaccines. Also, they are all using somewhat different assays to analyze the immune responses and have yet to be compared head-to-head with standardized assays.

Do these results, as well as those from Pfizer and BioNTech, suggest that mRNA is going to deliver on all of its promise as a vaccine platform?

This is really the only data that validates this platform, but it is fabulous news for this approach, with the caveat that we don’t know about the durability of the protection nor do we have long-term safety data. What we have seen on the safety data so far looks really promising. Most of the other mRNA vaccine candidates have only progressed through early phase clinical trials. Moderna has several other vaccine candidates in the clinic but they haven’t gone as far as the COVID vaccine candidate, and they certainly haven’t gone as fast.

How important is the difference in the temperature that is required for storage between the Moderna candidate and the Pfizer/BioNTech candidate?

The updated information Moderna released on stability is really important because it enables the use of the existing cold-chain apparatus to deliver the vaccine all over the world. Instead of requiring ultra-cold temperatures, this vaccine can be stored in a normal freezer for up to six months and remains stable for up to a month in a refrigerator. This is a really important observation.

It is exciting to think that very soon there will be two vaccines being considered for either Emergency Use Authorization or licensure by the FDA [U.S. Food and Drug Administration]. What will really matter is getting this vaccine into the arms of people, particularly those in the groups at highest risk, as soon as possible. Hopefully the good news continues!

Interview by Kristen Jill Abboud