What This Virus Expert Thinks About mRNA Vaccine Candidates for COVID-19

Pfizer (PFE -0.12%) and its German partner BioNTech (BNTX -0.27%) reported incredible efficacy data from a phase 3 trial for their mRNA coronavirus vaccine candidate. This news, paired with the equally impressive data from Moderna (MRNA -1.39%) about its candidate that takes a similar approach, inspired much hope around the world and injected optimism into the stock market.

We talked with Dr. Angela Rasmussen, a virologist and Associate Research Scientist at Columbia Center for Infection and Immunity, about what this exciting development means for the world and for investors.

Corinne Cardina: Fools, if you haven't heard, on Monday, Pfizer and BioNTech released a press release sharing new information about their COVID-19 vaccine candidate. So a little caveat. This data has not been peer-reviewed. This was a press release, it wasn't the raw data, but the market reacted very positively. It's been heralded as proof-of-concept for vaccines that take an mRNA approach. Right now, the early data indicates that the efficacy, meaning that it accomplishes the goal of preventing COVID-19 disease, it's more than 90%. For context, the Food and Drug Administration (FDA) had said 50% would be good enough. Dr. Angela, can you tell us a little bit about this news and what it means?

Dr. Angela Rasmussen: Yes, this news is very encouraging. But I'd like to caution people that we should be a little hesitant to jump to conclusions that this is a complete game changer. The reason for that is that, so this trial enrolled almost 44,000 participants in this Phase 3 clinical trial. This interim data analysis was based on what are called events. An event is when somebody in a clinical trial, either in the control group which receives the placebo or in the group that receives the vaccine, gets a case of COVID. In this case they're looking at symptomatic COVID-19 cases. So people who not only have COVID, but also have symptoms of COVID disease, so not asymptomatic people. This was based on 94 events. That's considerably less than the 44,000 that have been enrolled. We don't know about how many people within those 94 cases were in the most high-risk groups. Obviously, if this holds up, as the trial proceeds, there are more events that we can make conclusions about efficacy on that will be wonderful and that's performing much better than expected. Most of the vaccine candidates, people said 50% is good enough for the FDA. We think that it will be 70% protective. So this obviously exceeds that, which is wonderful news. But that could, of course, change as more events are added to this trial. It's going to be particularly important to make sure that some of the events are occurring in participants who are in those risks groups, especially elderly folks. One of the things about flu vaccines that happens a lot is that older people actually need to get a different formulation of the flu vaccine because their immune responses to the normal dose of the flu shot are not as robust as younger people. We need to make sure that not only is this vaccine 90% protective in all of the participants, but it's going to have that same efficacy in older people who are more at risk of severe COVID.