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Eric J. Topol, MD: Hello. This is Eric Topol for Medscape. It's a great privilege to have a one-on one conversation with my friend Paul Offit, MD, who is my go-to for vaccines. And this is an important time for vaccines. So, welcome, Paul.
Paul A. Offit, MD: Thank you, Eric.
Topol: We had convened recently to discuss vaccines. And then just last week there was a really important 9-hour meeting of the Vaccines and Related Biological Products Advisory Committee. Certainly, Paul, you were one of the key players there. Can you give us your overall sense of this long meeting, which was of intense public interest?
Offit: I think it was good that it was open, because what the public got to see was a look behind the curtain. What we struggled with is that typically for vaccines, one does large phase 3 trials, in which tens of thousands of people get the vaccine or don't get the vaccine. The data are evaluated and submitted as a biological license application (BLA) to the US Food and Drug Administration (FDA) for licensure.
But that's not this process. This process is not going to be a licensure process. These aren't going to be licensed vaccines. They're essentially going to be permitted for use through an emergency use authorization (EUA), which is frankly no different from any investigational drug. But that is odd because it's going to be given to most Americans.
I think from the public standpoint, when they hear EUA, they think hydroxychloroquine. Hydroxychloroquine was approved through an EUA, but it didn't work to treat or prevent the disease, and 10% of people who got it had cardiac toxicities. Or they think of convalescent plasma, also a product which has never been shown to work.
So the fear — and it's a reasonable fear, it's an understandable fear — is that the FDA, up to this point regarding these EUAs, really has not done its job. They have not stood between pharmaceutical companies and the American public to make sure that we get products that are safe and effective. They haven't. And therefore, the public is suspicious of this process.
What you saw in the advisory meeting last week, I thought, was an attempt to understand practically what the differences were going to be between doing it this way, with these unlicensed products, and doing it the way we always do. Because the fact of the matter is, these are large, prospective, placebo-controlled trials. The Johnson & Johnson trial is a 60,000-person trial. Pfizer's is 44,000. Moderna's is 30,000. That's a typical trial size for a biological license application. For example, the HPV vaccine was a 30,000-person trial. Our vaccine, the rotavirus vaccine, was a 70,000-person trial; pneumococcal vaccine was 35,000. So the size of these trials is typical. So why not do it through a biological license application? Why not do it the way we've always done it?
The answer is several-fold. Most important, I think the FDA would never license a product that was tested with a shorter period of time. I think that's the biggest. We're not going to know anything, really, about not just long-term efficacy, but even relatively short-term efficacy; we'll know that there's efficacy for months but not necessarily for a year. Whereas the HPV trial was a 7-year study and the rotavirus vaccine was a 4-year study. Usually it's several years. So this is unprecedented in terms of length of follow-up for efficacy and also, arguably more important, safety. We'll have a couple months of safety data after the last dose, which would pick up something like Guillain-Barré syndrome, as we saw with a flu vaccine. But you do worry about vaccine-induced pathology. And at least Stanley Perlman, MD, PhD, who was on the advisory meeting conference call, is a coronavirus immunologist. He wanted at least 4 months. So that's the struggle.
On the other hand, 225,000 people [in the United States] are dead from this virus within a year. As you move forward with these kinds of trials, you go from phase 1 to phase 2 to phase 3, you just try to reduce uncertainty. That's the goal. How much uncertainty do you need to reduce? Do we need to wait, for example, to see what the 1-year follow-up is, knowing that during that time hundreds of thousands of people may die? Should we wait 2 years, which William Haseltine, PhD, actually reasons: Why don't we wait 2 years and get all the data as we would do for a typical vaccine? The answer is because with the rotavirus trials, 60 children died per year; that's a little different from this.
Topol: Bill Haseltine was arguing during the advisory committee that we should wait 2 years for a vaccine?
Offit: No; it was just in a recent media interview.
Topol: Oh, okay. I didn't think he was weighing in on the committee. He's said some unusual things when I listen to his segments.
One of the reasons that an EUA is appropriate is, as you're putting it, the context of this pandemic, which is unlike the other vaccines that you reviewed. But another is that it takes many months to prepare a product BLA, right? They can be 10,000 pages. This is a much more expeditious route. Are there other reasons besides those two?
Offit: There's one other reason that was subtly stated on one of the slides presented by Jerry Weir, PhD, from the FDA, in regard to supervision regarding manufacturing. When the FDA licenses the product, they don't just license the product; they also license the process and they license the building. That is a rigorous process. I noticed that for our vaccine, the rotavirus vaccine, RotaTeq, was a 1-year process. You have to validate everything. You have to validate the computers; you have to validate how you're cleaning out the vats; you have to validate how you're putting the cells on a monolayer. However you're making the product, you have to validate every step of that. I think that in that slide that he showed, there was one word in there that made me think that this is a little looser than normal, which is the word "generally." It's going to be generally acceptable.
I asked somebody from the FDA to explain this to me, because when I looked at his slides, I thought, It doesn't look like it's any different in terms of what the FDA calls CMC, chemistry manufacturing control. It looked like it was no different from normal, which didn't make sense because I couldn't imagine how it could be that fast doing it the normal way. So there are some subtle differences there. But again, I wish we wouldn't call it an EUA. I wish we had another name for it.
Topol: Actually, that's an important point you brought up, because there is this pathway, expanded access, which could be used. What do you think about that?
Offit: Marion Gruber, PhD, who is at the FDA, talked about that as another way to think about this. And I think that makes sense. One of the fears she has, and I think we all have, is that Pfizer had stated that if they show that their vaccine meets a standard for efficacy, 50% or 60%, then they would then give the vaccine to the placebo group. She made the point in a couple of slides that they are under no obligation to do that — that under an emergency use authorization, you don't have to do that because, frankly, it's still investigational. It's an investigational product. Because the minute you give the vaccine to participants in the placebo group — and it could extend to other placebo-controlled trials — then you've lost data. Let's suppose that this vaccine is 60% effective. There may be vaccines out there that are 80% effective, 90% effective. But if you stop doing placebo-controlled trials, you're not going to know that. That's the tension in all of this.
Topol: This is one of the most important points of all: Once a company says their vaccine works and they file for an EUA, there is this ethical dilemma. I spoke to the Pfizer group, Kathrin Jansen and her colleagues, and their plan was, "We'll go ahead and file for an EUA. And we don't necessarily have to cross over our placebo participants, at least early on, because we certainly want to follow them." But there is an ethical dilemma. On the one hand, you're claiming some signal of efficacy; and on the other, you're denying the participants access to that efficacy. So it's a very fine line, right?
Offit: Yes. And there's not a clear answer to this. You could argue that if you're a 70-year-old person and you were in the placebo group — in the hopes that you were in the vaccine group — and now you find out that the vaccine is 60% effective or whatever, you can see how that person could reasonably say, "I think I should get this vaccine. I'm at higher risk. If I get this virus, I have a 10% chance of dying. I want this vaccine."
Topol: Yet here's this monstrous effort of having 60,000 people in a trial, but the follow-up can be basically lost if there's crossover. So it's like a domino effect. If one of these vaccines clicks and says, "We've got it" — and it looks like Pfizer and Moderna are leading at the moment — then there could be a rippling effect on all the programs, right?
Offit: Yes, because, ethically, can you give a placebo to somebody who's at risk — someone, say, who is obese or has diabetes or is older?
Topol: Clearly we're going to need lots of vaccines here. And as you alluded to, hopefully with incrementally increasing efficacy, even perhaps with a second generation of vaccines among these 200 different candidates. But is it a problem that people will ultimately take multiple vaccines along the way?
Offit: First, I think the only way we can immunize the whole population is with multiple vaccines. Second, I think it's going to depend on the vaccine. So let's suppose you received a replication-defective simian adenovirus or replication-defective human adenovirus vaccine. And then there was a different sort of replication-defective virus that looked much better, but it was also an adenovirus. There may be enough cross-reactivity where you wouldn't benefit from the second vaccine. But otherwise, for the most part, I think you would be able to have a second vaccine and benefit from it. For example, look at the shingles vaccines. Zostavax was given to people. Then Shingrix came along and it's a significantly better vaccine. And you can now get that even if you got Zostavax.
Superhuman Immune Responses
Topol: That brings up a topic that I think is really interesting that a lot of people don't appreciate outside of your specialty: the concept of superhuman immune response with vaccines. We've seen now some 30 or so well-documented reinfections with SARS-CoV-2 around the world with genomics to prove that the strain was different in the initial and subsequent infections, separated by months. And it wasn't the genomics of the virus evolving that was accounted for that; it truly was a reinfection. Now, of course, that's a small group among 40 million–plus infections. (The number is probably larger than 30, but many people don't have genomics to conclusively show that it's a reinfection.) The point being is that some people don't have an adequate immune response. We also know that from neutralizing antibody studies days after infection. There are some precedents whereby the vaccine could actually perform better than the typical human response. Can you take us through that? Because that's a key concept. I like to be optimistic and I'm hoping that the vaccines will be better than human responses. What do you think?
Offit: There's certainly historical precedent for vaccines being better than natural infection. The HPV vaccine induces a higher neutralizing antibody response than does natural infection — significantly higher. If you're infected with tetanus, you actually need to be vaccinated because the quantity of the tetanus toxin, so-called tetanospasmin, that causes symptoms is actually subimmunogenic. So you get symptoms without developing an immune response.
Similarly for children less than 2 years of age, by conjugating polysaccharides like the Haemophilus influenzae type B (HIB) polysaccharide or the pneumococcal polysaccharide to a harmless protein, you induce a T cell–dependent B-cell response. If you had just given the polysaccharide, which is basically what you're doing when you get naturally infected, that response doesn't happen. So actually those vaccines are better than natural infections. If you as a 6-month-old got a HIB infection, you still would benefit from getting a vaccine. Same thing with pneumococcus. So there are examples of that.
I think where that might happen here is that there were two papers in Science that looked at the capacity of this virus, SARS-CoV-2, to induce antibodies directed against interferon. In other words, it induces you to have an immune response against your own immune system. That's why people were worried at some level about convalescent plasma as having those kinds of antibodies, which could be immune-suppressive. I think this is a weird virus. Anybody who's been watching this for the past year should not make any predictions about what's about to happen because it's been so surprising. But I think you're right; I think we may be able to get a vaccine that is better than natural infection, because when you're naturally infected with the virus, it reproduces itself 10 times, 100 times, 1000 times. When you're given a purified protein or you're given a messenger RNA, which encodes just one protein of the virus, that doesn't happen. So we'll learn. I think we're going to learn as we go here. And I'm sure that some of this knowledge is going to be painful over the next couple years.
Building Better Vaccines
Topol: Do you think any of the different types of vaccines, whether it's genetic or protein, attenuated viral vectors, lend themselves to a more potent immune response or is it hard to know?
Offit: Well, technically, as a member of the FDA Vaccine Advisory Committee, I have to sign a form that says I never publicly expressed a preference for a vaccine, but I'll try and say it more generally.
If you were older, for example, over 65, and you look at the sort of Shingrix-Zostavax experience, Shingrix has two powerful adjuvants. One is based on this so-called QS-21, a saponin of the soapbark tree. The other is monophosphoryl lipid A from Salmonella minnesota. The purified protein product used in the SARS-CoV-2 Novavax vaccine actually has one of those adjuvants. So you wonder whether this so-called QS-21–like adjuvant would induce a better immune response. Similarly, I think the Sanofi-GSK collaborative vaccine also has a powerful adjuvant, a squalene-based adjuvant called AS03. As you get older, your immune system gets more and more senescent, so the powerful adjuvants may make a difference, as it did in Shingrix. But who knows? Let's see.
Topol: When we're in despair, we try to find the bright side of things. And the fact that there are these notable examples of vaccine programs that turned out to be better than what humans can mount as an immune response is really great to know. I don't think that's actually out there in the medical community very much yet.
Now for an update on another topic that we discussed previously. There are two points. You really brought this home — and today Tony Fauci and Andrea Lerner and colleagues published in JAMA on this — that just because we're starting on vaccines, we still have a long way to go. We still need to be wearing masks. The point being that you could be an asymptomatic carrier. You could be vaccinated so you don't get infected, but you still can harbor the virus in your nasal mucosa. Isn't that right?
Offit: There are many reasons to believe that natural infection with SARS-CoV-2 does appear to protect against moderate to severe disease associated with reinfection. Although there have been cases that people get a moderate to severe infection, get better, and then get a second moderate to severe infection. That is not typical. So it's unlike, say, strep throat, which you can get again and again, unmodified; or gonorrhea, which you can get again and again, unmodified. Those are examples where natural infection does not appear to protect against disease associated with rechallenge. That's not true here because what we're hearing is not that. What we're hearing typically is that someone got an infection and then later found out they had a mild form of the infection and was asymptomatic. That's the usual sort. And that's what you'd expect with this kind of virus. There were human challenge studies done in the early 1990s with human coronaviruses that found that you did get protection for a year, and the protection was generally against moderate to severe disease. Good. That's what you want. Knowing that natural infection appears to protect means that you can make a vaccine that can, in theory, induce an immune response similar to natural infection and therefore protect. So all good news.
But I do think that what you say is exactly right. Let's say you get a vaccine that is 75% effective at protecting against moderate to severe disease, which we'd all be happy with. That's still 1 out of 4 people — and you don't know who that is — who could still get moderate to severe disease.
Also, I think the vaccine will not be as good at preventing asymptomatic shedding or mild disease, because that's what the animal model studies teach us. The animal model studies teach us that you can prevent pneumonia, but you don't seem to prevent upper respiratory tract shedding. So you need to wear a mask.
That's what keeps me up at night: that a vaccine will be oversold as being a magical powder that we sprinkle over the United States and make all of this go away.
That's what worries me the most. People ask me what keeps me up at night. That's what keeps me up at night: that a vaccine will be oversold as being a magical powder that we sprinkle over the United States and make all of this go away. And people are going to say, "You know, I'm tired of the mask, I'm tired of social distancing." They throw it all away, engage in high-risk activity. And we take a step back.
Topol: I think that point is central. You emphasized that before but I wanted to get to it again, because I think a lot of people think the vaccine comes and the masks go, and we're looking at likely all of 2021 with masks. If you just judge the timeline where vaccines will ramp up and get to a large portion of people...
Transparency in the Process Is Key
Topol: That brings me to how to promote public trust. You've spent your career on vaccines and dealt with the resistance — the anti-vaxxers and all kinds of stuff. You've written books about this. If we were smart right now, and if you were to design a way to nurture public trust so that when the vaccines are approved and they have the data, we would get a high population-level immunity — what would we do right now to foster trust?
Offit: Right now, what we can do is be transparent with the process. I like that the FDA Vaccine Advisory Committee meeting was televised and anybody could log in and watch it. So they see people who are arguing about how this should work. There was a press conference after that meeting. One of the reporters said, "You know, it looks so contentious. Everybody seems so skeptical about the vaccine." That's what you want. You want everybody sitting around that table to be skeptical about this product. You want them to stand in the way in front of the American public and protect America. You want them to say, "I will approve this vaccine when I would get it, when my parents would get it. Would my children get it?" That's what you want to hear from those people. That's the way it works at the Advisory Committee for Immunization Practices (ACIP); I was a voting member there, too.
I think once the vaccine is in hand and you have some evidence that it works and it's safe, then you have to be able to tell people what you know and what you don't know. You know that it's effective for X length of time. You know that it's X percentage effective. You know that it's safe in this many people for this length of time. And here are all of the programs that are in place to continue to monitor safety, to continue to monitor for efficacy. Here's how we're going to continue to look at this. And then as it starts to roll out, 100,000 people have gotten it. A million people have gotten it. Ten million people have gotten it. And then you feel more and more safe. Maurice Hilleman, who I consider to be the father of modern vaccines, said it best: "I never breathe a sigh of relief until the first 3 million doses are out there." That's always true. So you never really quite know. Always just trying to reduce uncertainty, but you never eliminate uncertainty. You never know everything. The question is, when do you know enough to say that the benefits of this likely, very likely, outweigh the risk (and what is largely theoretical risk)?
Topol: If you were to guess, from what we know of the family of coronaviruses and as good as we can get with vaccines, do you think we'll be able to go longer than a year without people getting booster shots over time?
Offit: Yes. I'm willing to make any prediction as long as you don't hold me to it.
It's a single-stranded RNA virus. It certainly mutates like any single-stranded RNA virus. But both measles and flu are single-stranded RNA viruses. Flu mutates so much from one year to the next — or, frankly, from one minute to the next — that natural infection or immunization one year doesn't protect you the next year. I don't think that's going to be the case with this virus, although there have been people who've gotten two infections and there are genetic differences. The question is, and it hasn't really been answered yet, are there serotype differences or are these genetic differences, functional differences, that make the virus a different serotype or more virulent or less virulent or more contagious or less contagious? And that's the important question — not whether there are genetic differences; of course there are genetic differences.
Topol: So far this has been such a slowly evolving virus, except for the one mutation, the D614G mutation, that has become dominant. And even then, it's debated whether it is truly more pathogenic. I guess that that point of stable virus is good. But a concern is that it's hard enough to have people get, initially, a second dose of the shot, and then to have them come back every year to maintain a population immunity would be even harder. I think the other point that's worth noting is that if the vaccine has 60% efficacy vs 80% or 90%, then the proportion of the population that needs to be immunized is markedly different, right?
Offit: Yes, marginally. There is a formula for this. There are a few caveats, but if you had a vaccine that is 75% effective, you would need to vaccinate about two thirds of the American population to stop spread. But there are other things going on. First of all, 75% effective probably doesn't mean 75% effective against shedding.
But on the other hand, you do have some population immunity now. And also, hopefully people will continue to wear a mask despite the bad example that's being set by the administration.
Choose the Mask, Even With a Vaccine
Topol: No kidding about that. And how one can be anti-masking and pro-vaccine at the same time, just doesn't compute very well.
Offit: I was on service last week, and we take care of children who either have COVID-19 or are suspected of having COVID-19. If, when I walk into the room of someone who is suspected of having COVID, you gave me three choices: I can either stand 6 feet away (but if I don't stand 6 feet away I have to stand, say, within 2 feet of the person); I can wear a mask; or get a vaccine that's 75% effective. What would I choose? I choose standing 6 feet away first. Social distancing is the most powerful. Second, I would choose the mask. I think the mask, if worn correctly and the right mask — I'm not talking about an N95 respirator, but a good surgical mask that is well fitting — that's going to be more than 75% effective. The vaccine will be third, which is really the opposite of what the administration's pushing.
Topol: That probably is one of the most important things to emphasize. In a little way, [CDC Director Robert] Redfield made those comments during a congressional testimony and people said, "What? You'd rather have a mask than a vaccine?" But you articulated that somewhat better, which is not at all surprising to me, by the way.
What are your residual concerns at this time? We're going to see data from these trials, likely a couple of them, before year end. Fortunately, it's not going to be before the election in 8 days. It's going to be after. That got fixed, fortunately, by the FDA. That team developed a spine in the midst of all this. But perhaps we will see a couple of trials with readouts, and then we have a recommendation plan of phases of who should get vaccinated — kind of a staged process. What are your concerns about that going forward.
Offit: I worry about the interim analysis with small numbers — that Pfizer or Moderna will say, "Look, we've had 35 cases of illness and we're going to now report that. We have 25 or 30 cases in the placebo group, and four or five or 10 in the vaccine group."
I only hope that they don't submit for an EUA with small numbers. I really hope we get to 150, which is what the NIH group that was put together by Francis Collins had asked for. I think that's a minimum of what you need to at least feel comfortable that you have so-called tight confidence intervals for your efficacy.
Obviously, the worst thing you would do is put a vaccine out there that's unsafe. But if you put a vaccine out there that's ineffective, you are going to lose the trust of what is already a fragile confidence by the American public. You don't get a second chance to make a first impression. We need vaccines as our way out of this. And we can't screw that up. I do worry that the pressure to get something out there quickly, with small numbers, would put us, the FDA Vaccine Advisory Committee, in a position of having to say, "You just don't have enough data yet," even knowing that people are dying of this virus.
Topol: You've now brought up two key points about the first couple of trials. Not only can they affect the rippling of all the programs of vaccines by declaring efficacy and making it hard for people who are deemed at higher risk to stay on a placebo arm, but there's also this issue of incomplete ascertainment of what is really happening. And that would really be a problem.
When these companies have their data, will your group be reassembled to adjudicate that?
Offit: Yes.
Topol: And that will be a public hearing as well, right?
Offit: Both FDA and CDC advisory committees are always open to the public.
Topol: Even though Pfizer's trial is outside of Operation Warp Speed, they'll be reviewed by NIH as well?
Offit: Here's how it will work. The FDA vaccine advisory committee has already been asked to agree to three dates to meet in November and three dates to meet in December, in anticipation that there probably is going to be a situation where we need to review data. But all the FDA does is essentially permit the companies to sell — or in this case, distribute — the vaccine. But that's not the recommendation. It's the CDC that recommends vaccines through the ACIP. So the ACIP is going to independently review data and then make a recommendation.
Our hospital, like many hospitals, will wait for a recommendation from the ACIP. Usually insurance companies wait for the recommendation.
I think the ACIP really is the key group.
Professionals Are Skeptical of the FDA
Offit: What worries me in all this is that after the hydroxychloroquine and convalescent plasma experiences, it's not just that the public has gotten skittish about what's going on at the FDA. I think that professionals have too. So now you have at least five states that are going to form their own vaccine advisory committees. The National Medical Association, which is a group that represents African American physicians, has said the same thing: "We're going to get our own group of vaccine advisors. We don't trust the government." Which is to say that "we don't trust the FDA to protect us." If we've gotten to the point in America where we don't trust the FDA, we're in some trouble.
Topol: This is yet another essential point, because earlier we talked about how to promote trust. And what you've reviewed right from the top of our discussion today is that because of the precedent with hydroxychloroquine, which had no evidence basis, and then the convalescent plasma, with no evidence basis... And in the midst of that, a widening EUA for remdesivir, which had very little evidence, and now a full approval for remdesivir, which again has mixed results, including this recent WHO Solidarity Trial. How can the FDA approve it when you have a trial that negates the efficacy? So there is a trust lost in the FDA. But it seems, Paul, as though, in recent weeks, the FDA has gotten stronger. That is, it stood up to the pressure of Trump and the administration and Azar and the Department of Health and Human Services (HHS). Is that a sign that things are turning in the right direction?
Offit: Yes, most definitely. I think when Commissioner Hahn stood up and said, "No, we are getting 2 months of safety data after the last dose," which is a reasonable and minimal requirement, and typical, frankly, for vaccines — that clearly would have put the timeline beyond November 3rd, Election Day, which clearly aggravated others. But he wrote it down. He submitted it in written form to us to consider. And the administration backed away. And I think it did make the administration angry.
I think it may have made others who were higher up in HHS angry. But the fact of the matter is, Stephen Hahn stood up for the American public when he did that. So, good for him. And by turning to the FDA vaccine advisory committee, we're not government employees. We're academics. We will give our opinion. We're used to being in academic medicine. We're used to people ignoring our opinion all the time. But we can at least give an unvarnished, clear opinion about what we think about this, that that's what we'll do. We'll be honest about what we think of this. If we do that and that's in a public meeting, and then there's any attempt to try to go around what we've done, it would just backfire.
Topol: It's really great to hear your point on this. These are the most important clinical trials, as far as I can tell, in history, because we are in such a horrible predicament. We've dug this humongous hole in terms of how we're going to dig out when we have 83,000 cases a day for a couple of days in a row, and it's still on the rise. We're also seeing hospitalizations rise, and now deaths are increasing again. So we need a remedy. This is it. And we need to get it right. We've talked about all the things that could go off track if it's prematurely, or not properly, given the green light. So this has been a great discussion.
I hope that these other vulcanization of reviews in California, New York, and other states will start to get behind the FDA, that they'll realize that you and your colleagues and these different external groups that are reviewing the data, as well as internal at FDA, are doing it right.
We need to understand that this has gotten on course now in terms of the review process. That's really great. We needed that because we didn't have that last time we met. It was all up in the air as to what was going to happen, whether Trump was going to waive his vaccine approval as an election tool or not. I feel a lot better.
It's great to hear your views, Paul. Thanks for being with us. This has been a great conversation again. I think we have to have you back after your next review. There's no better way to understand what's going on than to get your expertise, your frank comments. Thank you so much for helping us at Medscape, and our community, get up to speed.
Offit: My pleasure. Thank you.
Eric J. Topol, MD, the editor-in-chief of Medscape, is one of the top 10 most cited researchers in medicine and frequently writes about technology in healthcare, including in his latest book, Deep Medicine: How Artificial Intelligence Can Make Healthcare Human Again.
Paul A. Offit, MD, is the director of the Vaccine Education Center at Children's Hospital of Philadelphia and the Maurice R. Hilleman Professor of Vaccinology at the Perelman School of Medicine at the University of Pennsylvania. An internationally recognized expert in virology and immunology, he has published more than 150 papers in medical and scientific journals and is the co-inventor of the rotavirus vaccine RotaTeq.
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