Even though Pfizer (NYSE:PFE) and Moderna (NASDAQ:MRNA) have won Emergency Use Authorization (EUA) for their respective COVID-19 vaccines, clinical studies of the vaccines are still ongoing. One key issue about these studies came up during the U.S. Food and Drug Administration (FDA) advisory committee review of Moderna's EUA submission. In this Motley Fool Live video recorded on Dec. 18, 2020, healthcare and cannabis bureau chief Corinne Cardina and Fool.com writer Keith Speights discuss the one major dilemma Moderna and Pfizer face with their COVID-19 vaccine trials.

Corinne Cardina: Keith, let's talk about some of the things that came up in this advisory panel. It was actually something that Dr. Gellin discussed, is what I want to start with. Unblinding. This is an interesting ethical question.

When you do have all these volunteers who gave their time and donated themselves to be part of these trials, then the FDA comes in and says, "Yeah, it's effective." These people are walking around in the world, and they're not vaccinated. So can you talk a little bit about what "unblinding the placebo arm" means and where the FDA stands on this?

Keith Speights: Sure. So these studies are what are called double-blinded studies. What that means is that the participants in the studies don't know whether or not they're receiving the actual vaccine or receiving placebo. Neither do the healthcare professionals administering the vaccines. They don't know it either.

The reason why it's set up that way is that prevents any bias from creeping in. There can be this placebo effect where you think you're getting a medication or a vaccine, and it causes your responses to be better than they ordinarily would. So that's why they do this double-blinding.

So the issue here is, all right, now we know that Moderna's vaccine, it appears to be safe and effective, highly effective. If you're in this study and it turns out that you received the placebo and not the vaccine, you really don't want to be walking around, like you said, Corinne, not being able to get the vaccine.

So what Moderna's wanting to do is they want to give the access immediately to these participants who were receiving the placebo. If they want to, that they could go ahead and get the actual vaccine. The FDA has a little dilemma there because they want to get more data. They want to study the effects of the vaccine versus people who didn't take the vaccine for a longer period of time. They're, I guess, more skittish about going along with Moderna's plans.

You're right, it's an ethical dilemma because people, they deserve to be able to choose whether or not they get this vaccine or not. I think it could be detrimental to future studies if participants who end up being in a placebo group don't have that option because I think it can make people in the future less likely to want to participate in these studies.

Corinne Cardina: Absolutely. There's pros to unblinding, there's cons to unblinding, so that will definitely be something to keep an eye on.

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