Eradicating polio

0:00Youth Mental Health is a complex challenge that requires comprehensive solutions. We must strengthen after-school programs. We must make digital literacy tools available in our schools. We must work with mental health professionals to support children. And we must empower mentors, educators, and parents to keep kids happy. Learn more about our commitment to finding lasting solutions at EmpowerOurFutureCoalition.com slash Solutions. Paid for by the Coalition to Empower Our Future. All engine running. I'm so genius. Get this. Welcome. Welcome. This is the show where we bring you science. What that essentially means is discovery of the questions we set. Technology unbelievable. Without further ado, this is the Naked Scientist. Hello, welcome to the Naked Scientist podcast. The program that brings you the biggest breakthroughs and also talks to the major movers and shakers in the words of science, technology, and medicine. I'm Chris Smith and this week we're going to be unpacking the efforts to eradicate polio.

1:13For much of the 20th century polio is one of the most feared diseases in the world. It's a highly infectious viral illness. In fact, there are a family of three separate polio viruses, all capable of invading the nervous system and in severe cases causing permanent paralysis and death, often through problems with breathing caused by respiratory muscle weakness. This was in fact how the iron lung came into being. At its peak, polio outbreaks paralyzed hundreds of thousands of people every year, including Franklin Roosevelt, who would go on to become the longest serving US president. Vaccination, however, has since transformed the picture, pushing the virus to the brink and eliminating it from all but a handful of regions. Because it is exclusively a human infection, it's also one that we can potentially eradicate for good and will unpack how health leaders internationally are making great strides towards that goal a bit later on. But first, let's find out what exactly is polio. Here's Katho Riley from the London School of Hygiene and Tropical Medicine.

2:16Polio is just like the shortened word for the the full name polio myelitis, which is the description of the disease that this particular virus causes. This pathogen, this virus, it infects just humans and actually a majority of the infections are essentially nothing to be concerned about, you know, you might not even know that you're infected, but for example, for every 200 infections, about one individual might have this polio myelitis. And so what this is, it's paralysis. And so typically, it's paralysis in the arms or the legs and a disease of children and a majority of settings. It also affected people's respiratory system, didn't it? Because that's where the iron lung came from, the whole idea of putting people in tubes that breathed for them because they just couldn't. Yeah, it goes into the brain stem and it's able to basically paralyze other parts of your system. But for these unfortunate individuals,

3:23the brain is no longer able to control the moving of the diaphragm. And so there were some really dramatic steps that were taken to put individuals in these or big chambers that would essentially control the air in their system so that it can force the lungs to breathe air in and out. But this was essentially the only way that someone could stay alive. Paul Alexander was the famous man in the iron lung. He died a couple of years ago. He spent his entire life, died at the age of 78. He was a lawyer. He was used to practice law from within his iron lung. How many people, obviously nowadays it's different. But when he was growing up, how many people would expect to catch polio in a country like the UK per year and either be in the category who end up with a serious problem with their nervous system versus just what we think of a non-serious infection to it? What do the numbers look like historically? We're not too sure, actually. One of the challenges is that

4:26this manifestation can be caused by a number of different pathogens. And so whilst we might be able to count paralysed individuals, we couldn't really say how many were caused by polio virus. However, at a global level that the estimates are prior to the introduction of vaccination, about 300,000 individuals, potentially up to a million. We really don't know. It's thankfully rare these days, but I mean, I'm not that old, but I remember as a child growing up, there was a lady who lived down the road from me who walked with a quite serious limp and she had had polio as a child. So I mean, it was a very visible manifestation in those days. What can you tell us about the actual age in itself? You've said the humans are the only natural host for polio virus, but what actually is it? Where does it come from? How do we catch it, etc? It's a tiny, tiny little virus. Virologists refer to it as fecal oral transmission,

5:26but essentially what this means is that it's found in poo. I got a small daughter currently, and I was trying to change her nappy this morning. She was not helping at all. And it just made me think about how easy it is for basically stuffing poo to be transmitted into your hands. If you're not washing your hands before you've prepared food, then you might accidentally consume some of that contamination. And so it's this kind of natural process, really. That results in spread of virus from one person to another. Okay, so it gets where you'd rather it didn't. You eat it effectively. Yeah. Once it's in the mouth, where do the virus particles go next? So it goes in the same place where your breakfast might be going. So down into your guts, and so the virus is able to infect you, basically it attaches to your cells in your stomach, and once the virus is able to infect you, it can then start to multiply inside you. And viruses

6:30do this very clever thing where they take advantage of your cell machinery to reproduce more viruses. You know, you might only need a small number of viruses to be consumed for you to basically become a virus factory. So it goes down your throat, replicates in the lining of the intestine, so it can get out of the body and do what your daughter did this morning. And spread. But in the process, it then presumably in some people, it's into the bloodstream, and that's going to take it to other organs, which can include the central nervous system. And that's the origin of the paralysis is it gets into the nervous system. Exactly. And and virologists and pathologists think that this almost might be a horrible accident. If we think about it from the virus's perspective, there's no benefit to cause paralysis in individuals. If anything, you're less likely to be infectious once you're paralyzed. Were there any treatments that could be thrown at this,

7:33or we can throw at cases? Cause this is still going on around the world, isn't it? In some places unfortunately, this is happening on a daily basis. Are there any treatments we can throw at this, or once you get that paralysis, is that it? Well, once you get the paralysis, it is pretty much permanent. Going back to the 1950s and 60s, there was this setup of a charity in the United States called the March of Dimes. So Franklin D. Roosevelt was someone who acquired polio relatively late on in life. And and he was determined to develop treatments for individuals that have developed this paralysis. So a lot of this is a lot of therapy. So physiotherapy and also improving how individuals can make use of these limbs, even though they might have less ability to sort of use their muscles. It might become less severe over time with this therapy and with age, but it really was a pretty permanent paralysis.

8:37Catho Riley at the London School of Hygiene and Tropical Medicine there. Now as Cath mentioned, vaccines have been game changers at the forefront of the global fight against polio, turning what was once a devastating disease into one that is now largely preventable. The vaccines work by building a lifelong immunity to the virus. So even if we do run into it, any infection is trivial. Through their use, we're now closer than ever before to eradicating polio. But developing and delivering vaccines isn't straightforward. Vaccines based on weakened live forms of polio are very effective, but they're also seeding potentially viable viruses back into the environment, making eradication paradoxically more tricky in the long run. Vaccines based on killed polio virus, on the other hand, are safer, but they're harder to administer and they may have an overall lower coverage. There is, however, potentially a third way. A new generation of vaccine that is extremely good at driving a powerful immune response

9:38becomes without the risk of it being a live virus. It's called a VLP, virus-like particle. It's basically just the outer shell of a polio virus. Nicholas Stonehouse, a virologist at the University of Leeds, has been developing it. I asked her first, though, to explain the background to the existing polio vaccines. So there are two sorts of vaccines. There are what we call the oral polio vaccine and the inactivator, the oral one. Many others who are sort of, let's say, over 40 will have had. This is like a little drop on your tongue and this is a virus which has really had the stuffing knocked out of it. The immune system still recognises it as polio, but it doesn't cause disease or it shouldn't cause disease. When you say it's had the stuffing knocked out of it, it's live. It still infects, but it doesn't cause disease. That's right. So yeah, so it can still

10:40infect, which is why you can take it in the same way as you actually still would be infected by polio, that's, you know, through the mouth. So it can get inside the body, it can replicate more copies of the virus can be made, which actually makes it a very effective vaccine, but it can't cause disease. There are three polio viruses out there, naturally, are all of them in the vaccine, and we can form like that. There are different formulations over time that have been used, but in order to do those, all that earlier eradication, then yes, it was a mixture of the three different types of polio. Unfortunately, there's not cross-protection. So in a worst-case scenario, you can have polio three times if you don't have those three different types in your vaccine. We no longer see types two and types three in the wild. We only see type one, but we do see some vaccine-derived polio cases. And what are they? And is that the reason why we have killed vaccine

11:47now? Because there was a big change, wasn't there? It's been 15, 20 years ago now, but we stopped using live vaccine like you've been describing in countries like the UK in favor of a killed vaccine. Is that the reason? Some countries still use live vaccine. Some countries in fact have never used a live vaccine. So it's that it is a complicated transition, but there is a risk of a live vaccine, and of whatever sort converting back to causing disease. And this can be from an event where there's what we call recombination, where there are very similar viruses that are circulating around, which are not causing disease, but there can be a kind of joining, if you like, of those viruses with the vaccine, and that can result in the vaccine regaining some virulence along with mutation. It's very, very rare, but it happens. And when we use these live vaccines, how do they actually protect us? What do they do that means that when we do encounter polio for real, if we do,

12:53we don't succumb to it. So we believe that the main protection for polio are antibodies. So the immune response that's generated to the vaccines means that the body produces antibodies, and that memory is retained so that if you then get infected again, that memory response means that you produce antibodies quickly, and you can combat the disease. So actually I think some vaccines don't give you long-term immunity, whereas vaccines like polio that we have as children actually then protect us for the rest of our lives. And is that the rationale for using live vaccines still then, rather than killed ones, because we get longer-term protection, so it's a more agile intervention? No, not necessarily. So the vaccines that are live can replicate, so they are still producing more, more virus particles, more vaccine, if you like,

13:55in the body, and they do that in the gut. So you get a sort of a gut response, which is much more native, it's much more normal, and that gives you better protection. So it gives you what we call mucosa immunity. It also means you can spread that person to person, which can be also very helpful. That's intriguing. So you're saying, if I get the live polio vaccine, I can actually infect you with my vaccine and protect you as well. So there's a degree of a wider envelope of coverage than just the people you immediately give the vaccine to. Absolutely, and unfortunately, therefore if that vaccine has mutated, you spread in the same way, yes. Ouch. So we now have this combination of live vaccines, which are still used, but we've reduced their use in some geographies to avoid this risk of them reverting back to a virulent form, but we're still using them in some places. We have a killed version, which can't do that,

14:57and therefore ideally we'd like to just use that, but we can't use it everywhere quite yet, so that we need to transition between the two. What's your other option that you're now able to put on the table? What we've been trying to do over the last 15 years or so is to produce what we call virus-like particles, something that the immune system will see as a virus, but it contains no genetic material. So it hasn't been made from virus, it's never been in contact with viruses, and therefore is completely safe both to make and also to use. In essence, then, it's a bit like an empty husk. It's the, it looks like a virus, the immune system thinks it's a virus, but it has no ability to make more virus, therefore it cannot cause disease. Yep, yeah, it's an empty shell. Can you make it then? So it sounds very straightforward, doesn't it, so you think why goodness has

15:59this taken 15 years? Because normally you would have the container or the husk as you mentioned it full of genetic material, and that partly stabilizes it, it stops it getting deformed. So if we have no genetic material, we have to put in some stabilizing mutations into the virus surface, into the capsid structure, in order to stabilize that and mean the shape doesn't change, and therefore the immune system really does see this as a virus, and also we make this just from protein, which we make in different expression systems, we can use plants, we can use yeast, we can use insect cells, because these are cheap manufacturing systems. If you're going to make a vaccine that's going to be used worldwide, and it's also going to be compatible with current childhood vaccines, it's got to be cheap. In essence then, you program yeast or insect cells

17:03to make the outer coat of the polio virus, but there's no innards, but because there's no innards, it would be unstable and deformed, so you have found ways to engineer some changes, to effectively add some struts to prop things open, so it stays strong, and it stays looking like a virus right to where the immune system can see it, ingenious. This makes the structure more stable to temperature, because quite often vaccines are not very temperature stable, and if you think about the challenges of trying to vaccinate in some parts of the world, where the external temperatures can be very high, then everything's got to be kept cold. These particles that we've generated are really quite firmly stable, so you can heat them up, and they don't change, they are nice, they stay as we want them to be. The proof, of course, is in the pudding, or the proof is in the eating, in some respects, it's not a normal vaccine, this one, though, is it,

18:05is it any good? How have you tested this? Polio is exclusively a human infection, so how have you tested this works, and at what stage are you out with, with now deploying this into the end going to eradicate polio? Animal experiments have been done at the Medical Health Regulation Agency, so MHRA, and they show neutralizing antibody tighter, so the amount of, if you like, good antibodies that are generated per amount of vaccine, and the aim that we had would be to generate antibodies that were as good or better than the current vaccines that are in use, those inactivated vaccines, and that's what we've achieved. Nicholas Stonehouse at the University of Leeds, and Nicola thinks that pretty soon she should have a workable solution that could well be ready to play a part in pushing polio to extinction worldwide. We wish her luck. Youth mental health is a complex challenge that requires comprehensive solutions.

19:08We must strengthen after-school programs. We must make digital literacy tools available in our schools. We must work with mental health professionals to support children, and we must empower mentors, educators, and parents to keep kids happy. Learn more about our commitment to finding lasting solutions at EmpowerOurFutureCoalition.com slash Solutions. Paid for by the Coalition to Empower Our Future. The Naked Scientist Podcast is produced in association with Spitfire. Cost-effective voice, internet, and IP engineering services for UK businesses. Find out how Spitfire can empower your company at Spitfire.co.uk. Music in the program is sponsored by Epidemic Sound, perfect music for audio and video productions. This is the Naked Scientist Podcast with me Chris Smith, and today we are exploring the global effort to eradicate polio. Now, while polio has been eliminated from most parts of the

20:11world, the virus is still circulating in a handful of places. Today, regions of Afghanistan and Pakistan continue to see ongoing transmission of wild polio virus. However, there's hope, because some countries with very similar challenges to the aforementioned have already successfully eliminated the virus. But why exactly does polio persist in these neighboring Asian nations? Here's Saber Wadood, who's at the World Health Organization. In 2024, we had 99 cases of 41st type 1 in both these countries. Last year in 2025, the count is at now stands at 44, including 31 cases in Pakistan and 13 from Afghanistan. Now, if I zoom in further, there are three places, two in Pakistan and one in Afghanistan. Cosmopolitan and city of Karachi, that a number of people would have heard of, very famous city of this region. Certain areas and population groups are harboring polio virus, and in 2025,

21:18the program did not detect any analytic case of polio in Karachi. It was all through environmental surveillance, but the detailed analysis and the labs and the genomic sequencing of those viruses indicate that there is local transmission that are going on. The second place is another geography in Pakistan called South Hepatumquat, which is at the border of Afghanistan, very insecurity that is leading to lack of full functional access to all the children to be vaccinated on a consistent basis that's lacking and hence we are not able to build a population unity up to the levels that required for stopping the transmission of virus. And the third place is the southern region of Afghanistan, where again, the challenges mostly linked to security related dynamics and full functional access in the local context to all the children on a consistent basis and hence the

22:24population unity through vaccination dryers would not be built up to the levels that required to eradicate polio virus. Are those difficulties surmountable in your view? Because if we've got polio anywhere, people often say well then it's everywhere because with the global population being as mobile as it is these days, we cannot afford for it to be anywhere. So we've got to get to it everywhere. Is this doable? Polio has been eradicated from places like young, places like South Sudan, places like Northern Nigeria and the places that I was referring to at very similar challenges when it comes to the unstable security situation and lying out of challenges of insecurity and access challenges. Polio program in those places demonstrated working closely with the local communities and going beyond community engagement to the level of community ownership where people would know how important polio vaccine is. Encouraging

23:28news isn't it? Zabaya would do it there from the World Health Organization. Now as we just heard, eradication means stopping the virus everywhere and keeping it from coming back. That requires sustained vaccination campaigns but also constant vigilance and surveillance in communities and via sewage systems and also rapid responses to any new outbreaks. The final phase can often be the hardest but if successful polio would join smallpox as one of the very few diseases ever eradicated worldwide. So how might this be achieved? Well I've been speaking with Ananda Bandier Padier who's a medical epidemiologist at the Gates Foundation. Wild polio virus two and wild polio virus three have been fortified eradicated which basically means you can't find a trace of these wild viruses, these two specific serotypes anywhere in the world. So that basically means we have only one wild type left, the wild type one and the fact that we've been able to eradicate

24:36two of the three and it's steady-radicated those two. That must give you confidence that it is possible to get this over the line and go for the last one. Absolutely so the proof of concept is decisively there. It's not just these two wild polio types being gone but they have not come back. We have established the vaccination efforts in a way that these viruses once they have been stopped. There's no way they can actually come back and reinfect communities. So absolutely yes the proof of concept both of eradicating different types of polio viruses and sustaining that eradication status is very much there. What do you think our chances are are we going to get this over the line because ever since I was at university and that was a little while ago now people have been saying

25:36we're getting so close to eradicating polio and every time we don't quite make it are we going to do it this time and by when do you think we'll be waving the flag and saying we've done it. I keep referring back to sports when I talk about eradication. If you're a sports fan Chris disease eradication is the Olympics of it. If global health is a sport then eradicating a disease is clearly the World Cup or the Olympics. It's the ultimate goal of any public health initiative and not all the pathogens can be eradicated. Polio is clearly one such pathogen that can be eradicated from a virologic perspective and then from a tool perspective we have we have everything that we need to get to the finish line but the difficulties remain it's not an easy task to get rid of a pathogen once and for all and as you know there has been only one human

26:42disease that we have been able to eradicate. So it remains a very difficult and complex task. There are many challenges including the challenges of the difficult geographies the challenges with the virus itself. It's a notoriously smart virus. It finds our most fragile settings and most vulnerable settings all the time. We also need a unified global and sustained effort to essentially keep pushing to reach that finish line but I think again given the fact that a eradication itself has been one of the most challenging tasks for global health it's not surprising actually that we are very close but there's still a few meters left that we need to cross across the thousands of miles that we have already crossed with 1,000 cases of paralysis being reported in the 1980s before

27:44the eradication campaign started. That was per day right that was the 1,000 a day on average. Correct 1,000 cases of paralysis from polio per day from the world to where we are right now where out of the three wild type viruses two are gone more than 99% of the geographies are free. So the trajectory is very clear but that shouldn't underestimate the challenges that remain ahead of us and the only way to overcome those challenges is to get united and remain united as a global community from a funding perspective, from a scientific perspective, from a policy perspective to really reach that finish line and to ensure we have the science and the policy backing us to sustain that achievement. And when we do achieve it how will we keep an eye on things and for how long so that we know we really have achieved it? When will we feel finally happy to say

28:49polio is eradicated? Yeah that's a great question and there are multiple examples as to how we know that the virus circulation has really been decisively stopped. There are proven surveillance strategies that include tracking of all cases of acute onset, flasad paralysis which basically means the muscles are weak and lose from the virus infection. So we do that acute flasad paralysis which support from the national governments and WHO accredited laboratories across the world. We also do sewage surveillance or wastewater surveillance for polio virus circulation monitoring. So essentially strategic areas of different countries they collect the sewage samples they send it to the WHO accredited laboratories and then polio virus presence

29:51is confirmed or ruled out. These two forms the cornerstone of the surveillance system and that will continue after we see the last virus being detected from the existing sources of the virus outbreaks and you see an example like India which had its last case of paralytic polio detected in 2011 and then for the past 15 years it has been maintaining sensitive surveillance systems through these primary modalities that I just mentioned, syndromic paralytic surveillance and the wastewater or sewage surveillance and based out of the data that are coming in from those sources we can save with confidence that India as an example has been polio free for 15 years. And then the Bandia Padier from the Gates Foundation there. So it looks a face value very encouraging

30:53doesn't it too of the three naturally occurring polio viruses have already been globally eradicated so our approach can clearly work and now just one form of the virus remains in pockets of a couple of countries the figures speak for themselves don't they fewer than 50 documented cases last year the problem that confronts us though is that political instability and conflict are the biggest enemies of public health and a glance at any newspaper confirms that with what is going on at the moment we're very likely to be creating more opportunities in the weeks ahead for the polio genie to escape from the bottle again globally and before we finish ramming in the cork let's hope that doesn't happen and that we can end this decade with polio consigned to the past that is it for this week we're back with you on Friday with a look at the latest science news stories for the week in the meantime we will have updates as usual on LinkedIn and also on Instagram do please leave us a review on apple on Spotify and wherever you get your podcasts and a very big

31:54thank you to those of you who are stepping up to support this program with your donations if you like what we do and you can help us do please head over to nakedscientist.com forward slash donate i'm Chris Smith thanks for listening and for more of us here at the Naked Scientist team until next time goodbye youth mental health is a complex challenge that requires comprehensive solutions we must strengthen after school programs we must make digital literacy tools available in our schools we must work with mental health professionals to support children and we must empower mentors educators and parents to keep kids happy learn more about our commitment to finding lasting solutions at empower our future coalition dot com slash solutions paid for by the coalition to empower