How do vaccines work? What happens when new diseases emerge? Why are outbreaks of nearly eradicated diseases happening in 2019? Pediatrician and vaccine scientist Dr. Peter Hotez explains.
Peter Jay Hotez, M.D., Ph.D., is the founding dean for the National School of Tropical Medicine at Baylor College of Medicine. He is also a professor in the departments of pediatrics and molecular virology & microbiology. He is a health policy scholar in Baylor’s Center for Medical Ethics and Health Policy and co-director of the Texas Children’s Hospital Center for Vaccine Development.
Learn more about the National School of Tropical Medicine at Baylor College of Medicine.
For links referenced in this episode:
Outbreak: A Tale of Vaccines in 2019 | Transcript
Erin: Welcome to Body of Work, an exploration of health topics in the news and important issues facing science with experts from Baylor College of Medicine. I'm Erin Blair, and my guest today is pediatrician and vaccine scientist Dr. Peter Hotez.
Let's just get right down to brass tacks. How do vaccines for infectious diseases work?
Dr. Hotez: Well, vaccines work by stimulating the immune system to produce either antibodies or immune cells in order to fight infection. So let me give you an example: the polio vaccine. The polio vaccine is made by either working with the actual poliovirus that's either inactivated or killed using various substances or passage several times through cells in the laboratory in order to weaken it. So that when an individual gets the polio vaccine, they're getting a weakened version of the virus or a killed version of the virus that stimulates an immune response, but it protects you against getting real polio as you go about your day to day activities. Same with the measles virus vaccine. So the measles virus is one of the great killers of children globally. At one time, 2.6 million children died every year of measles. The virus was weakened in the laboratory, and then you administer that weakened virus, so you don't actually get measles, but it protects you from getting measles in the future. Then there are other vaccines that work, either they're developed through genetic engineering, like some of the vaccines we're developing. Our recombinant protein vaccines done through engineering, so it codes a part of the organism. So the bottom line is vaccines are either the entire organism that's weakened or killed or a part of the organism that then stimulate an immune response and prevent you from getting infected.
Erin: How do vaccines work on a community level?
Dr. Hotez: Well, what happens is if you vaccinate large populations at the same time, you can actually interrupt transmission of the disease. So for instance, with the measles vaccine, and today we combine the measles vaccine with the mumps vaccine and the rubella vaccine, that's why we call it MMR. That MMR vaccine, if given to more than 90 or 95 percent of the population, will actually stop the possibility of any transmission of real measles virus circulating in the community. Sometimes we refer to this as herd immunity and it's very effective it also means though that if you want to stop these diseases from returning, you know we eliminated measles in the year 2000, if you want to stop it from returning, we have to have 90 to 95 percent of the local population vaccinated, and that's why measles now is come back in 2019. We've had more than a thousand measles cases in America. It's because we have large pockets in the United States now where significant numbers of kids are not getting their MMR vaccine, and that leaves an opening for the real measles virus to come back.
Erin: So we don't have the whole herd protected?
Dr. Hotez: That's right, so nationally we're still doing pretty well, but in places such as Brooklyn, New York, or in Portland, Oregon, or even some cities here in Texas, such as Austin, and Plano Texas, we have significant pockets where there's measles, either has come back, or there's a high likelihood it will come back.
Erin: How has the advent of vaccines changed healthcare in America?
Dr. Hotez: Well, it's made us less fearful of deadly infectious diseases. So for instance, if you were a parent in the United States in the late 1940s, early 1950s, we had terrible polio epidemics in our cities every summer because the poliovirus thrives most in the summer, so that parents lived in fear that their children would become paralyzed or even die from polio. And now parents no longer have to live with that fear. So our modern vaccines really came online, beginning in the late 50s, and going into the 60s, 70s, and 80s, and 90s, and now we have several vaccines so that parents no longer have to worry about their children dying of these diseases. I'll give you a very personal example when I was a pediatric house officer, a resident in Boston, I was on the children's service of the Massachusetts General Hospital. We were admitting a child every couple of weeks with a devastating infection called H flu meningitis, haemophilus influenza type B meningitis. It has the word influenza in it because back in 1918 when during the flu pandemic people erroneously thought that bacteria was the cause of flu. It wasn't, but the name stuck instead it causes a terrible form of meningitis and, I would as a pediatric resident, I would admit a child every two weeks to my service with that devastating disease, and some children actually perished, they died. Others were permanently injured with neurologic injury, like deafness. It was really devastating and took a big emotional toll, not only on the families but also the house staff as well. And that was in the late 1980s, but then the new vaccine came online, the H flu vaccine called the HIB vaccine, H I B, and as a consequence of that, the disease disappeared from the United States so that by the time I was a young assistant professor of pediatrics in the Yale University School of Medicine, the disease was no longer around. So I would teach the next generation of house staff pediatric residents about HIB disease purely for historic interests, just like the old timers would talk to me at Mass General about diphtheria and tetanus, I could tell them the same tales about HIB disease, that that's the power of the vaccine.
Erin: It's remarkable. Has that same sort of effect been seen on a global level?
Dr. Hotez: Absolutely, so the big push really started in the year 2000 when new organizations were created, including the Bill and Melinda Gates Foundation, and their big first tranche of money, 750 million dollars, went towards forming what's known as GAVI, the Global Alliance for Vaccines and Immunization. And the idea was we could do better vaccinating the world's children against diseases like HIB, and measles, and diphtheria, and polio, and at the same time introduced two new vaccines for rotavirus infection and pneumococcal pneumonia and meningitis. And we've made great strides, great progress, so now what we've seen is at that time in 2000, roughly half a million kids were dying every year of measles. For the first time in 2017, it decreased below a hundred thousand. So still, a lot of kids dying but you know eighty-ninety percent reductions and deaths from diseases like measles and HIB and pertussis which is whooping cough, so that's of tremendous excitement.
Erin: You founded the National School of Tropical Medicine at Baylor College of Medicine. What constitutes a neglected tropical disease?
Dr. Hotez: So the term neglected tropical diseases, or NTD's, is a term that we help shape, coin, and shape the framework for in the early 2000s, and it had to do with the fact that there was a lot of excitement because of GAVI for childhood infections as well as some other diseases like HIV/AIDS, and malaria, but there was a whole group of other infectious diseases that literally got named "other diseases" as part of the U.N. Millennium Development Goals and having something called "other diseases" was a non-starter. Nobody was going to get very excited, so a group of us who worked on chronic and debilitating parasitic diseases like hook worm infection, and schistosomiasis, and leishmaniosis, and Chagas disease got together and went about and did a branding exercise called the neglected tropical diseases and we came down, a group of us came down from Washington D.C. to Houston to Baylor College of Medicine to form a whole school around these poverty related diseases. And it's called the National School of Tropical Medicine, which is pioneering innovations for these diseases with a big focus on developing vaccines. Because these are poverty related diseases - they only occur among the world's poorest people, you can't make money on these vaccines, so there was no point in trying to create a company around it. So we're doing it in the nonprofit sector, funded by external grants, and now we've advanced several vaccines into clinical trials for neglected tropical diseases, where we're quite excited about that.
Erin: Are there neglected tropical diseases in the United States?
Dr. Hotez: Yeah, absolutely. We first looked at this framework of neglected tropical diseases. The focus was very much Africa, Asia and the poorest parts of Latin America, but then by moving to Houston in Texas, we started looking around and found a depth and breadth of poverty here that we never knew existed. And one of the things that I've learned over the years, wherever there's extreme poverty, you find neglected tropical diseases. We began to look with our faculty, and what we have found is impressive. We have found the transmission of Chagas disease, which is a parasitic infection of the heart. We found viruses transmitted by mosquito, as everyone knows about West Nile virus infection, but we have dengue fever transmission in Texas, as well as even some Zika transmission in 2016 and 2017. We have typhus, which is serious, and Rickettsia L infection transmitted by fleas, we have parasitic worm infection - so the point being we made the case that Texas is actually a disease endemic country because we have the confluence of a number of factors that help neglected tropical diseases emerge everywhere, so we have the confluence of extreme poverty and low-quality housing and lack of access to good, clean water, or sanitary services, but also climate change is affecting our state together with human migrations and of aggressive urbanization, and all of those are creating the perfect storm to allow neglected tropical diseases to form. So we've actually now have taken on one of these here in Texas for a vaccine. So we're developing now a vaccine for Chagas disease. This is a done a partnership with my long-term collaborator Maria Elena Bottazzi, who’s also a professor of the National School of Tropical Medicine and the associate dean of our school.
Erin: What happens when a new outbreak comes on the scene - an Ebola virus, Zika?
Dr. Hotez: Well you know, what happens when a new pathogen is introduced to a community is, in many cases they've never experienced disease with that pathogen before, so there is what's said to be immunologically naïve, they have no antibodies or other immune defenses against those organisms ,and they can spread through a community very quickly. We saw this with Zika in 2016 in the Western Hemisphere, where Zika affected large segments of the population in Brazil and then it moved up into Venezuela and Colombia, into Central America, and then into the Caribbean so that island of Puerto Rico got hit very hard with Zika virus infection and it caused a not only debilitating illness, but also birth defects as well. And so we saw lots of babies born with congenital Zika syndrome which includes small head microcephaly, and it's a very devastating condition. So there was a lot of worry that South Texas and South Florida were vulnerable because of that confluence of the things we're talking about, poverty and climate change and human migrations, and sure enough, we did have some Zika transmission in South Texas. Not as bad as we had feared, but we'll see, Zika still could come back.
Erin: How are new vaccines for new diseases developed?
Dr. Hotez: Well we go through quite a lengthy process, and one of the unique features about our vaccine center at the National School of Tropical Medicine, and it's done as a partnership with Texas Children's Hospital - we call it the Texas Children's Center for Vaccine Development - is we’ll often take a vaccine all the way from discovery through scale-up process development and manufacture. We then to shepherd the vaccine along for what's called toxicology testing and moving it into the clinic by filing an Investigational New Drug application with the Food and Drug Administration an IND, and then getting permission to move into clinical trials and we'll take it through clinical trials as well. So it's a unique facility especially for an academic health center, not many academic health centers have the ability to translate, and that's the term that's often used now, to translate a molecule or a vaccine all the way from discovery into clinical development, so we're very excited about that.
Erin: How is vaccine science adapting and innovating for the future?
Dr. Hotez: Well, there's a few things that have to happen. One of the problems are the timelines are long, right? So, for instance, the hookworm vaccine that is now in clinical trials in Africa and Latin America, I started working on that vaccine as an M.D./Ph.D. student in 1980s, so these are biblical time frames right, and it could be 30 years. The schistosomiasis vaccine was a little faster, we started working that in the early 2000s. So there's a need for innovation to streamline the development, but it's not easy because remember how vaccines work, we're often immunizing well individuals to prevent them from getting these infections, so the safety bar has to be very high and pristine. And so these vaccines have to go through a lot of safety testing, first in preclinical laboratory animal models, and then the slowly graded clinical trials phase 1, phase 2 phase 3. That's why I'm often aghast when I hear the anti-vaccine lobby claim that vaccines are not adequately safety tested. These products are the most extensively safety tested pharmaceuticals on the planet, often taking decades of clinical testing, but we're trying to now look at some cutting-edge biotechnologies and apply them to our neglected disease pathogens for purposes of vaccine development, and a lot of that work is going on here at Baylor College of Medicine - things like single-cell RNA sequencing, or systems biology, or gene editing. And so we're trying to apply all those technologies to our vaccines, but we also need innovation, and how we do clinical testing to maybe do more things in parallel, so we don't have this decade, several decades, of clinical testing we could streamline that down a few years.
Erin: Why are outbreaks of nearly eradicated diseases taking place in 2019?
Dr. Hotez: So, isn't it terrible? We've seen now the return of measles in 2019, and we know why. This is happening because there's been decline, local declines, in vaccine coverage in many counties in the U.S. So measles is often the first one to come back, because it's most highly transmissible of the viruses that we know about. It has what's called a reproductive number of 12 to 18. That means if a single individual has measles, on average 12 to 18 other people will get it, particularly infants under the age of 12 months, not yet old enough to get vaccinated. And that happens because the virus lingers in the atmosphere and lives on surfaces. So it's very easy to acquire measles, and now measles is back in the United States. We eliminated it in 2000, and we're going on 20 years and now we've had more than a thousand cases, so that's very discouraging, and it's happened number one due to declines in local vaccine coverage, and that in turn has happened because of the rise of a very aggressive, well organized, and well-funded anti-vaccine movement that we now have here in the United States, that's convinced parents that vaccines cause autism and other things which is absolutely not true. But what the anti-vaccine lobby has done is to create an impressive, in a bad sense, misinformation campaign. So we have this tragic situation now in the state of Texas where there's over sixty thousand kids not getting their vaccines, and so it's only a matter of time before we, our state, suffers from measles outbreak just like we've seen in New York State this year, and in Washington State earlier this year.
Erin: Your most recent book "Vaccines did not Cause Rachel's Autism," draws on your personal life and your connection to current misconceptions about vaccines. Can you tell us more about that?
Dr. Hotez: Sure, and I wrote the book in part because of what I saw happening in Texas with this dramatic rise and the number of kids not getting their vaccines. I'm a vaccine scientist and pediatrician, but I'm also, along with my wife, a parent of four adult children including Rachel, who is 26 years old and has autism and number of intellectual disabilities. And because the anti-vaccine lobby centers their misinformation around the phony claim that vaccines cause autism, I felt that I was perfectly positioned to stand up to this and wrote the book. Vaccines Did Not Cause Rachel's Autism came out late last year, published by Johns Hopkins University Press, and what it does is it goes into some detail explaining the evidence showing there's absolutely no link between vaccines and autism, but also explaining what autism is, and how we have identified more than 99 genes involved in early fetal brain development that are linked to autism. And one of the things that we were able to do here at Baylor College of Medicine with the excellent Genetics department here, is do whole exome sequencing, and Rachel and my wife and I, we were able to identify one of those genes. So it's very powerful technology. The point being, these processes that result in autism are happening in early fetal brain development, well before kids ever see vaccines. So the book really explains the evidence not only that vaccines don't cause autism, but the lack of plausibility because of the fact that autism is already underway in pregnancy well before kids are ever vaccinated.
Erin: Why do you think there is such distrust between the scientific community and the lay population when it comes to vaccines?
Dr. Hotez: Well you know, we've got a situation that, part of the reason why the anti-vaccine movement is allowed to gain ascendancy is because they're running unopposed. The scientific community has been mostly invisible or silent. That's the reason why I wrote the book, and one of the things I realized, both working on the book and being out there in the public defending vaccines, is that we don't hear from our scientists. That the scientific community is very focused on writing and speaking for each other and focusing on grants, and papers, and laboratory meetings, that we no longer see public engagement as a worthwhile activity or we don't even know how to start engaging the public. And I don't have a lot of evidence to support it but there are some interesting studies like that one done by the Research America policy group think tank in Washington that finds that 81% of Americans cannot name a living scientist. And so essentially, the American public has really no idea of what we do, and what our activities are like, and I'll partly blame our profession on that. We're too inward looking, and we don't see public engagement as a vital activity. So I've been writing and speaking about the importance of building in science communication into Ph.D. training, building health communication into medical training both at the doctoral level and the postdoctoral residency level. We've got to figure out how to turn this around and get the scientific community out there and engage so that people recognize scientists and so scientists again become a household term.
Erin: Almost having to reclaim your authority, redevelop confidence in the public.
Dr. Hotez: That absolutely right because right now, the public has no role models to identify. When was the last time you saw a scientist on cable news, or you know really profiled in the media? I mean, I think Baylor College of Medicine does a pretty good job getting our scientists out there, but we don't have the bandwidth needed to really match the bandwidth of this very aggressive, well-oiled, anti-vaccine lobby, and its 500 websites all amplified on social media and e-commerce platforms.
Erin: What questions should people ask their healthcare providers when it comes to vaccines?
Dr. Hotez: Well, I think it's important to remember that you have an expert in your community. That expert’s called your pediatrician. Pediatricians spend a lot of their training learning about vaccines, how to administer vaccines, how to use vaccines, how to schedule vaccines, and so take advantage of having a pediatrician in your community and have that conversation with them. There's certainly other sources of vaccine information. The CDC website, the Centers for Disease Control website, has got some good information, but the problem is it's a little hard to mine. It's a very dense website. I think that's one of the other lessons that we're seeing from this aggressive rise of the anti-vaccine movement, that we don't have easy to deliver information for parents. That's one of the reasons that I also in the book, in the epilogue of the book, I list the major phony assertions of the anti-vaccine lobby and talking points to provide the quick-time the information needed to counter the misinformation.
We seem to be losing the battle against this anti-vaccine lobby, and I think we've now got to take steps to counter it, and I have a few ideas of what I think we need to do. I think, for instance in states like Texas, we have to close vaccine loopholes. Right now if you're a parent, you can opt your kid out of getting vaccinated for reasons of personal or philosophical belief. I'd like to shut that down. I'd like to make vaccines compulsory if you want to send your child to public school. In the past, your child had to be vaccinated, I'd like to bring that back, here as well as in the 18 other states that allow non-medical exemptions for reasons of personal or philosophical belief. This was done in California. California allowed vaccine exemptions, they had a horrific measles epidemic in 2014-2015, the California Legislature said we're not going to do this anymore and they shut down the non-medical vaccine exemptions. We need to do the same in Texas, as well as a number of other states in the U.S. But that's not going to win hearts and minds, so we're going to have to figure out, one how to rebuild a system of robust vaccine advocacy in this country, but at the same time we have to dismantle a lot of the misinformation. So it'll take time, but I think it's doable. I think we can bring us back to the old normal. So the new normal is our parents aren't vaccinating their kids, we've got to flip that around, go back to the future as they say, and make vaccinations the new normal again.
Erin: Thank you for tuning into Body of Work by Baylor College of Medicine. If you enjoyed this episode, be sure to subscribe, and be on the lookout for our next episode, where we'll talk with Dr. Sharmila Anandasabapathy about how technology is changing global health.
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