What are coronavirus vaccine clinical trials designed to show, and what they are not designed to show? Dr. Bruce Gellin of the Sabin Vaccine Institute joined Corinne Cardina and Olivia Zitkus of Fool.com's Healthcare and Cannabis Bureau on a Dec. 18 episode of Fool Live, where he discussed vaccine safety and efficacy, and why it will take some time for us to understand how well new vaccines from Moderna (NASDAQ:MRNA) and the Pfizer (NYSE:PFE)-BioNTech (NASDAQ:BNTX) team curb the spread of the coronavirus.


Olivia Zitkus: On the vaccine itself, we're wondering: There's been a little bit of confusion as to whether the vaccines from Moderna and Pfizer and all these other companies, prevent people from getting infected with the coronavirus, or prevent someone who is already infected from developing the disease caused by COVID-19. Can you help clarify what the vaccine actually accomplishes, and how it impacts the spread?

Dr. Bruce Gellin: What it actually accomplishes is different than what the studies are designed to show what was shown. So what was provided to the FDA and to the thousands of people, I think they've got to about 15,000 at some point, who are watching. What the efficacy of the vaccines were. There are some safety as well, but this is efficacy, where essentially this large group of people, for Moderna it was 30,000 people, 15,000 got the vaccine, 15,000 got the placebo, and then to see what happens to them. Is that comparison of what happens to those people who are immunized is what this efficacy is about. Most of the disease that was seen was in the placebo group, which tells you the vaccine was doing something. That's what it's designed to show as that demonstration. What it can't show directly is whether or not the vaccine effects infectivity. Can you still transmit the virus even if you are protected from getting if you are infected. Those are studies which are more complex and not really amenable to these clinical trials that are looking at what individual experiences are, but those are the studies that we put in place, more epidemiologic studies to try to determine transmission. The public health method for now is, this is an incredible story about vaccine science. Vaccines are now starting to roll, unless you've been in a cave, you've seen these pictures of aisle's and a dry ice, and trucks, and people getting in line. But until we know more broadly how the vaccines are performing in the real-world and particularly when more people are vaccinated and there's immunity in the population, only that we know how well it's going to dampen transmission, the ongoing spread of disease. We're confident that this is the beginning of the end in terms of technology that's now providing that immunity, and we'll just have to continue to look at what's happening and adjust the strategy based on how the vaccines are performing.

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