If you decided to invest in coronavirus vaccine companies in 2020, you've been in for a wild ride -- and it's not over yet. Earlier this month, a vaccine from the team of Pfizer (PFE 0.12%) and BioNTech (BNTX 2.42%), closely followed by Moderna's (MRNA 3.49%) candidate, officially won the vaccine race when they were authorized for emergency use by the U.S. Food and Drug Administration. But many other companies are still working to bring coronavirus vaccines to market, and there are plenty of logistical challenges ahead. Dr. Bruce Gellin, President of Global Immunization at 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 to talk about what is left to learn about coronavirus vaccines and what investors should watch for.

Corinne Cardina: Hi Fools, I'm Corinne Cardina. I'm the Bureau Chief of Healthcare and Cannabis on Fool.com, and I'm here today with Olivia Zitkus, an editor and analyst on Fool.com, also in the Healthcare and Cannabis Bureau. We are so excited to welcome Dr. Bruce Gellin, President of Global immunization at the Sabin Vaccine Institute. Fools, we are going to spend the next 30 minutes discussing COVID-19 vaccine development, the challenges of distribution and the ultimate goal of vaccinating the world against this horrible disease. I do want to remind everyone we're using a question and answer service called Slido, so you can open that up. Our code is MFLive. Submit your questions and we will try to get those answers for you. Dr. Gellin, welcome to Fool Live, we're so excited to have you. How are you today? You've got to unmute your video, there you go.

Dr. Bruce Gellin: Thanks for having me, I got a sneak preview of some of the previous shows. That was fun.

Cardina: Great. Why don't we start with a brief introduction about what you do, your background and what the Sabin Institute is.

Gellin: Thanks. I'm Bruce Gellin, I'm currently at Sabin Vaccine Institute, it's a non-profit in Washington. It focuses on global immunization, primarily trying to think about access to vaccines for lower and middle income countries. I've been there for about three-and-a-half years, and before that, I spent 15 years at the federal government running what's called the National Vaccine Program Office, where I was trying to keep all the arms and legs of government that deal with vaccines and vaccination, trying to keep them working in the same general direction.

Olivia Zitkus: Fantastic, thank you so much for that introduction. I'm excited to jump in, I think we're going to start just by talking about some vaccine use from the past two-ish weeks. Just last week, an FDA advisory committee reviewed Pfizer and BioNTech's vaccine candidate, and the FDA granted an emergency use authorization. Now, frontline healthcare workers have already begin receiving the vaccine this week. Yesterday, the committee reconvened to look at Moderna's vaccine candidate and ultimately they voted to recommend authorizations for this vaccine as well. Last night, the FDA confirmed that it would work toward granting that UA, which we're expecting some time today hopefully. Of course, broadly, this panel of independent experts are looking at safety and efficacy. But Dr. Gellin, we're wondering on a more granular level, what these experts are evaluating in terms of these vaccines.

Gellin: Thanks for doing this. I mean, I thought since I have the vaccines 24-7, I thought I was the only one who realize vaccines were in the news all the time. Now, they're in the news all the time. As I suspected, there will be other issues that you want to talk about. But most recently are these two meetings over the past few weeks from the FDA's advisory committee. I think the couple of things about that are really important. One is the fact that there is such a thing as an advisory committee. An outside experts comes together in public, which is also not something any other country does, to take a look at the data, kick the tires, ask questions of the manufacturer, ask questions of the FDA and give their advice, so what the FDA might do. That's why people are a little confused that this is an advisory committee that provides advice. Is the FDA who decides, makes decisions. What we saw last week and what we're going to see probably later today or early tomorrow, is the FDA's decision about the authorization of another vaccine for COVID.

Zitkus: Great, thank you. In terms of what they're looking for and discussing in these meetings. Corinne and I were talking about how they were streaming them live on YouTube, and you could just hop on whenever you wanted. A lot of the discussion was around age groups, that the vaccine is designed to treat diversity of participants and the trials. Are there other issues that are top of mind that we could be looking for?

Gellin: What they do and all of this information is out there and it's not so easy to digest. But all the information is out there a couple of days before, which is essentially almost the complete data package from the manufacturer. Things that they don't allow for the public or don't provide to the public are proprietary issues about manufacturing techniques. For the rest of it is, all the data they want the FDA to see to make a decision about moving a vaccine forward. The focus was largely on these Phase III clinical trials, which are these pivotal trials to determine how well a vaccine actually works. Built on top of all the other information that the companies have collected from animal studies, and laboratory studies, and earlier phase studies, and give a sense of the immune response and the safety of the vaccine. It's that totality of information at the advisory committee was asked to say, given all that, what do you think? Is this a vaccine that we should be allowed to be used more broadly in these emergency situations.

Zitkus: Great. Okay, thank you. 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?

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.

Zitkus: Awesome. Thank you. Things are looking up. Both of these vaccines are mRNA vaccines, messenger RNA vaccines. While the two mRNA vaccines are intended to be a two-dose regimen, you vaccinate a person and then they return three or four weeks later depending on the vaccine for their second dose, some people are wondering about the potential for just one dose of these mRNA vaccines. Notably an opinion article in the New York Times published just today, I believe this morning, questioned the possibility of getting more people vaccinated by administering just one of the two intended doses. I'm wondering what your thoughts are on this, and what is the impact of these kinds of conversations on the public's behavior?

Gellin: It's an important question. I think that part of this is recognizing, I mean there are 300 different approaches that are being taken globally and you probably tracking every one of those, but I think what's interesting is that there's so much interest, so much attention. Any scientist who has an approach to vaccine has come forward, and we're going to learn a lot from that. Not all 300 horses are going to end the race, but I think we're going to learn a lot in that process. But as far as this one and two dose, there are a couple of companies that are focusing on a single dose. I think that's really important when you think about usability. For a program standpoint, finding a person for the first time to get vaccinated is hard enough, getting them to come back when they need to is really a much more complicated challenge which we're going to have to deal with to try to make sure we provide protection. But the question that's really important, what was intriguing, and I think that's probably the best you can say from the data was that both of these mRNA vaccines are two-dose vaccines. The initial clinical trials of phase 1 and phase 2 trials are designed to determine what's the right dose, what's the right dose interval, and it shows that the maximum immune response is after two doses. But because they were looking intensively in these studies, you could follow-up people after that first dose, and you saw that about the two-week mark, 10 days, 14 days, there was a splitting in the curve. What that means is that at about 14 days, some people even after first dose seem to be protected when compared to the placebo. Interesting, encouraging, but very small numbers. While we've seen these what's called a point estimate, when you compare those numbers, it is in the 50-ish percentages, that's intriguing but since there's such small numbers, a confidence limit, as statisticians say is quite wide, and if there was one or two differences in those who is in the placebo group or not, it will be quite different. The short story is until we know a lot more, two doses is what we need, and giving them a first dose could actually cause a difficulty if people don't get the full immunity they need. In doing so, we'll be using a lot of vaccines that might not be protecting the population as we think.

Zitkus: Right, that length of the immunity is still a question with the two-dose vaccine. If we have people just getting one dose of a two dose schedule then that really complicates the data picture.

Gellin: In fact, so looking at the immunology of coronaviruses and other vaccines, we don't expect lifelong protection but maybe we'll be surprised. Given what we know about vaccinology and immune response, a second dose is likely to give a better and longer response.

Zitkus: Great. What kind of data and information will you be watching for that gives us clues about the length of immunity, or on that same vein about viral mutations that could affect how the vaccine works overtime?

Gellin: Those are two different questions. I think what we're going to be looking for is what's often heard is breakthrough; people who are vaccinated and then still get infected. Based on the efficacy numbers, we don't expect to see many of those cases. But there will be some because it's not a hundred percent effective, it's in the 90, 95, and that maybe different in the real world where things are not managed exactly as they are as meticulously in a clinical trial. But then the question is what happens as we follow-up people who've been vaccinated and have an infection? We'll have to look to see is there something about that virus that has escaped the immunity that's provided by the vaccine. That will give us some suggestion, if you will, about whether or not some of the mutations that have been seen are significant. Right now, though we've been seeing those mutations, it doesn't appear to change either the clinical picture of the disease or how the vaccine might work. We have to keep an eye on that. I think watching these breakthrough cases when they occur will give us a sense both in terms of resistance and the duration of protection.

Zitkus: Great. Thank you. As an expert on these vaccines, are you encouraged by the future of the mRNA platform for vaccine production and development?

Gellin: It's really exciting. The other part about this is that mRNA vaccine technology was not invented when this pandemic began. This is a technology that's been explored for some time for a range of things from cancer to other immune responses, and now its time had come. So it's very encouraging. I think everybody was more than pleasantly surprised at how well it worked. Based on the previous studies, nobody was surprised we could create this immune response. We've seen that with other coronaviruses, we've seen that with other viruses. These companies have portfolios that are looking at other things as well, and we can understand that this is an approach that will provide immunity, but until you do the clinical trials, you don't actually know whether that immunity correlates with protection. So for those reasons it's very attractive. I think we might be lured into thinking we solve all the problems because mRNA is going to answer all our problems. It's likely to answer some, but I don't think it's going to answer all, which is why I am encouraged by the wealth of other technologies that are out there that might or might not work for coronavirus but might emerge for other problems that we have.

Zitkus: Great. Beyond these two mRNA vaccines that the FDA advisory committee has reviewed, are there any other candidates now still on trial basis that you find particularly promising? You alluded to a one-dose vaccine earlier in the chat a few minutes ago.

Gellin: I love the headlines. Helen Branswell who writes for Stat and covers this headline, although they never write the headlines, somebody else does that, talked about the tortoise and the hare, and I thought this is an important reminder. We're watching now the hare, those who for a lot of reasons have come out hard and fast, keep an eye on the tortoises as well. I think when you think about that, we'll look at some of the things that maybe are not front-and-center right now, technologies are still emerging. But when I looked at this, we want to look at not just the technology, but a feasibility. We've learned a lot in watching the size of situation about a vaccine has got incredible performance. But it's really a bear to operationalize. Which so we've seen these trucks, we've seen freezers, we've seen dry ice. You guys are probably investing in all those different technologies related to that. Quite clearly, this is a complicated vaccine to deliver. The logisticians are on it and they're going to do their best on it. But it's clear when you think about broad availability, not just the United States but around the world, things that are simpler are going to matter. So I'm looking at those things, things that are one dose rather than two. Things that can be given, maybe oral, or through mucosal route, nasal spray rather than injection. Doing those things, I think are going to be game changers. Another one is the requirement for temperature. If you can have the product stable, you can already project how much easier just to get things around. I think there's a broad portfolio of those, a lot of different approaches taken, but I think as trying to think of the future in terms of the feasibility of the long term. Because I think we're going to need these kind of vaccines for the long term. I don't think we're going to eradicate this virus. We're going to need to learn to live with it.

Zitkus: Right. Yeah, we've got the one dose vaccine in the trial basis from Johnson & Johnson (JNJ -0.14%) our investors at the Motley Fool probably heard plenty about Novavax (NVAX 7.71%) this year, which is exploring a host pandemic combination flu and coronavirus vaccine, and then an oral tablet from Vaxart (VXRT 9.77%). So there are all these other possibilities that make Pfizer's extra cold required vaccine look a little bit more complicated in the real world.

Gellin: In a lot of ways. It's probably lucky that they came out of the box first, because further along, people will say, "Oh man that's hard." But because of the urgency, because of the performance, you are going to have to make hard work. But I think over time we will have to be looking at the approaches that provides both the protection but also make it an easier vaccine to deliver.

Zitkus: Turning from that, the vaccine race to the vaccination challenge. What other issues do you see? Maybe either than cold chain two-dose schedule? Do you see any potential confusion if two similar vaccines are in the market?

Gellin: I think in the near-term, I think that at least in the United States, the way that work speed is managing this, and supplies are limited I don't think there'll be multiple products in the same marketplaces. So I think if the opportunity for confusion will be less because they will be placing vaccines in certain places, if you're customer, I'm not sure you're going to be so excited about that. You may not be able to choose. You take what's there. As the situation changes and as supply is increased, then there'll be many different products. I think that will be confusing and important to sort out which are the right vaccines for the right people at the right time. We deal with that a little bit with influenza. Fifteen, 20 years ago, we had just a few products now we have many, which is good for public health and good for individual health, but makes it complicated from a market standpoint, it's hard for people to know exactly how to keep the right inventory of who their patients are and the like. But yes it will be confusing, and keeping the communications clear is going to be important. Hopefully, some of the information technology will help us with this. Some things have been created for this and we'll have to see how well they work. But I'm trying to get people back from the second dose to make sure they get the correct second dose, and not just anything that's out there is going to be treated as well.

Zitkus: Great. For those vaccines that are still in those earlier stages of development that might not be getting the attention that Pfizer and Moderna are getting right now, there are still lots of them out there, how easy or difficult do you think it will be to enroll people in those clinical trials now that another vaccine has received emergency use authorization and vaccinations have started?

Gellin: That's really an important question. That was a large part of the discussion of the FDA advisory committee yesterday, and these are marathon sessions. Nine hours of Zoom is a lot for anybody, but they spend a lot of time asking committee for their advice on how to go forward, just where we are right now. The short story is that right now people were randomized in the current vaccine trials to either receive the vaccine or placebo. Well, now, if you receive the placebo, which you shouldn't know, but maybe you do because of your reactions, but you receive a placebo, you think, "Well, wait a minute, I'm walking at random. Why don't I get protected?" There is this question about the ethical obligation. Some of the companies fail to provide the protection for those people versus the fact that you're going to lose a lot of information if you un-blind the studies and have people now all be vaccinated, so it was a large part of that discussion. I think that in the near-term, this is not going to be such a problem because with relatively small supplies, it shouldn't be so difficult to enroll people in a study if they're not going to get vaccine for very long. I know we'll probably talk about that, that New York Times think about where you are in line. But it's going to be a while, so maybe there's going to be an incentive for people to enroll in the study if they think they can get a vaccine as part of that study. Overtime, that's getting more complicated. I think the answer to that, which is easy to say but hard to do is, is the science part, that if we can come up with what are called these correlates of protection. What can you measure in a laboratory that says, if you have this level of antibody or if you have this level of T-cell or level of something, you are protected. Right now, we don't have that. We know relatively how that works, but that's why the clinical trials are done. If we could figure out these correlates of protection, then we wouldn't have to have these massive trials, and we will know in a smaller subset of people if some other experimental vaccine will provide this kind of protection.

Zitkus: Great. Yeah. I'd love to turn to that timeline and herd immunity idea. Herd immunity is when a critical mass of the population becomes immune to a pathogen. Ideally, through vaccination, not through infection and the spread dies out. I'll start here, if you could predict the timeline for when the US could reach herd immunity, what would be your most optimistic guess for what has to happen to get there?

Gellin: I'm going to hedge on this one because it's not about the calendar, but it is about the supply. I can give you some date, but if there aren't supplies to try to vaccinate people or if people aren't interested in getting vaccinated, then any of these projections are fanciful. The herd immunity is, now everybody has heard about that. A lot of people think it might be herd mentality. The herd immunity idea is that when there's enough people who are protected in a population because they're immune, either from having been infected from the natural virus or from a vaccine, from a virus standpoint, you are looking for people who you can infect. If more and more people in the community are protected, they have that shield in front of them or immunity, the virus has no place to go. That's the point when you start to see the virus will taper off, and essentially it has no place to go. Since it's only going to be infecting humans, that's for the herd immunity threshold. People throw around all kinds of numbers for that, from high numbers, from 70-85, some people think lower numbers. If you think about how many people are mixing in the population and agree that that affects transmission, the short story is it's going to take an overwhelming number of people, probably two-thirds of the population to be immune to start to see these effects. You can do the math. You hear all kinds of projections about supply, but just over the past day or two, we've heard about disruptions in the supply so you don't know. The same time, there are other vaccines coming in that could increase that supply. It's a long way of saying, who knows. But if you want a date, I would say that by late spring, we should have a sense of where we are. That doesn't mean we're there, but I think we should at least have a sense, if not across the country, in communities how this is playing out to get a sense of how well this is happening. Again, learning both about the saturation of the population and the effects that vaccine might have on transmission. If it turns out that the vaccine stops transmission, that's a different story because we're going to then decrease the number of people who are spreading their virus. If a vaccine reduces your chance of getting sick but you're still infected and still have the ability to transmit asymptomatically, then that's a different problem where you still could have more virus in the community.

Zitkus: The New York Times interactive article that you mentioned a few minutes ago, I was surprised to see, well maybe not all that surprised, the number of people in front of me in line for a vaccine based on my age, my health profile, all those things, that was published a few weeks ago. In the District of Columbia, I am behind 76,000 other people in line to get a vaccine and behind 23 million people personally across the United States to get a coronavirus vaccine. I think Corinne took the test, too.

Gellin: I thought you'd be further back.

Cardina: I am. Olivia has her health issues complicated. I'm behind 278,000 others. So that's probably a little bit more typical of someone in our age group. Have you taken the quiz?

Gellin: I agree. I'm staying a little bit in front of you, but not too far. But it's just making thing. You probably saw that on CNN a couple of weeks ago that Sanjay put that out there for Anderson Cooper and say, "Here are your numbers." He's looked up and he was behind I think 268 million people, and he goes, "How many people are there in the United States?" I think it's a helpful sense of all that. Just to get into that a little bit, because there's been a lot of discussion before the vaccine came and now that it's here, who gets to be at the front of the line. As we've seen now it's healthcare workers, people in long-term care facilities and those who care in long-term care facilities, that's around 26 million people. The next couple of categories are essential workers, so any guesses on how many essential workers there are in the United States, including the two of you?

Cardina: We're not essential workers. 100 million?

Gellin: Don't tell your bosses that.

Zitkus: We won't.

Gellin: I mean, the number of essential workers-and I think it's an important thing and everyone can make a case for why they're essential, whether you're a food handler, you're in transportation, a teacher, information technology, a Motley Fool podcaster, it's all out there -- but it's 87 million people. When you watch this, I think that's what we're going to see next, is really attention over who should get to go next in line. Because frankly, every one of the people who are essential can make an argument for why they are essential, or at least most can. Until the supplies are large enough, there'll be some jockeying for who gets to go next. But beyond that are more of the traditional recommendations for vaccines about people who are at risk for severe disease and underlying conditions. Adults with high-risk medical conditions, 100 million in United States. Obesity, hypertension, diabetes, kidney cancer, smoking, other things, 100 million people. Then adults after that, adults over 65 are 63 million, and then there's the rest of you. So that's how it stages out. It's interesting to watch other countries do this in different ways. The UK is focusing on the elderly first, and we're going to see how this plays out in different countries. I don't think that there will be differences among the states, although the governors apparently have some flexibility to be able to make some of those adjustments. We'll start to see that soon when more vaccine's available, and we get into these populations beyond these well-defined healthcare personnel and long-term care.

Cardina: Absolutely. That number that I read off earlier, just to be clear, that is my line in DC. So based on my risk profile, I am in line behind 144 million people across the US. Olivia, she is number 23,000,001 in the US, so she is just a little bit ahead of me, but I didn't want to confuse anyone with those more localized numbers. Looking ahead, looking down the line, once we do have a significant portion of the population in America vaccinated, what do you think the world is going to look like once this herd immunity, whatever it looks like, is reached? Is it going to be important to continue wearing masks and social distancing for the foreseeable future?

Gellin: I hope not for the foreseeable future, but for the near-term future, I think so. For the very near-term future, I mean, right now absolutely. I do worry a little bit up to think, vaccine here, problem solved, time to go out, and it happens to be the holidays. Right now, this is not the time to, as everyone was saying, because it's such a critical time when we're having this disease escalation. I think it might look like how we handle influenza maybe a little differently. I think that probably we're going to see people, masks will not go away entirely. I suspect we're going to see a different way of maybe respiratory etiquette where people might be wearing masks in the winter time. I've seen that in other countries where in the winter time people wear masks for a variety of reasons, either to protect themselves or to protect others, I think we're going to see some of that. I think people are going to be thinking twice about where they sit and who they are around and who the air they're exchanging with and maybe try to be a little more cautious. Hopefully, we're not going to become paranoid because of that, but I think we'll be more cognizant of that. What I don't know, and that's maybe what you guys have been exploring is, are there some other technologies that are going to come out here that's going to help us with that? Francis Collins, who runs the National Institutes of Health, it's a little bit facetious to joke that maybe we're going to need to have a coronavirus diagnostic in our toothbrush. So every morning you'll know whether or not it's OK for you to go out if this is such a strange virus where you can be asymptomatic and spread. So I think there will be things like that. It's going to be a different normal. Then quickly on the vaccine side, I think we're going to learn a lot from what we learned in these past 11 months on how we can move a lot more nimbly, a lot more quickly to develop products that we need and not wait for five and 10 years, it has been historical.

Cardina: Absolutely. So, Dr. Gellin, our last question for you today is that, of course, we know you are a doctor. But at The Motley Fool, we're investors. Could you share some advice to anyone who is thinking about putting their money in one or more of these leaders in coronavirus vaccine development?

Gellin: So I knew that was coming. I've seen how this goes and you know what the answers are from people like me. The hare is what everybody can see. I think I would look at the tortoises and see what their technologies are, particularly, those that offer something that is going to make it easier to become protected. So oral, mucosal, I think there's a lot in there. The things that need every one dose rather than multiple doses. Things don't really require this unbelievably, complex cold chain. Things that might be stable in various temperatures, either hot or cold. Those are the things to look at. You can look at all those lists and see the kinds of criteria they have. But I think it's also important to look at the companies that are doing these. What we've seen is the range of new partnerships that had to come together. People with the technology, with those who have some sort of experience with the regulatory apparatus, as well as those who have some business sense. So I think that's where your analysts are going to be much better than anything I know, looking at those, and trying to layer in where there's promising technology for all the reasons of making this simpler. Because I think innovation is about simplicity, so the more than that can happen, the better. Then make sure that these are the companies that have the wherewithal to keep going.

Cardina: Absolutely. You just squeezed a bunch of investing tips into that one answer, so we appreciate that. Thank you so much, Dr. Gellin. We appreciate you spending your Friday with us, and we will keep in touch.

Gellin: Thanks for including me. Thanks a lot.