War Against Smallpox: Edward Jenner and the Global Spread of Vaccination

Imagine, if you will, a new virus spreading around the world. In 1800 it spread from England to Western Europe and the Atlantic seaboard. By 1805 it had encircled the world and indeed reached the borders of China from three sources. From India through the South China Sea, from Mexico across the Pacific through the Philippines, and from Russia through Siberia. By this time several million people have been infected in all continents including South America, South Africa and Australasia. The virus... Michael, sorry to interrupt. I'm just going to say I don't think you're showing your slides. You might want to just try sharing your screen again. Showing the screen again? Yes, there we go. It's come back. Thank you. Aha, I need to go back. The virus, or rather the disease caused by it, had first been observed about 50 years earlier. Like many new viruses it emerged from man's contact with animals. It was first found not in wet markets in China but in less than salubrious dairy farms in England. Its growing profile from the late 1760s can probably be attributed to the growing scale of the dairy industry at a time of demographic and economic growth. It was generally found on the udders of cows, with the virus probably communicated on the hands of dairy maids and farm workers. It was called cowpox but that caused the cow no real distress and the ultimate source of the disease remains a mystery. It caused a minor problem for human beings when the virus lodged itself in a scratch on the hand or the arm. A person infected with cowpox experienced soreness and swelling and a pustule appeared at the inoculation site that there was no other danger. The patient seemed not to be infectious, a point that underlines the oddness of positing a cowpox pandemic. The truth is that its global spread occurred only because people took a lot of trouble to preserve cowpox lymph and transmit it around the world. The rationale was that cowpox infection gave people protection from a far worse disease, the most dreaded disease of the age, smallpox. Cowpox, denominated in Latin as variola vaccina, was not only the first vaccine but the original of all vaccines. If cowpox was a novelty, smallpox was all too well known. The relationship of variola virus to humankind goes back several thousand years and it is so close a relationship that the virus wholly depends on human beings for its life cycle and transmission. It enters the body through the nose or mouth, nests in the lymph nodes and gets into the bloodstream. There is a high fever, an outbreak of vesicles that fill up with lymph. The number of spots can be so great that they merge together giving what's called confluent smallpox, which was really deadly. It appears that smallpox had become more virulent in the early modern period as it spread around the globe and became one of the major sources of morbidity and mortality in the old world and then in the new world. It was a major cause of death and the case fatality rate was around one in eight, though it often in particular savage epidemics was one in four. In the late 18th century in Britain it was responsible for 36,000 deaths each year on average. That is of course about a hundred deaths a day and of course here we're looking at day to day in the course of the year, we're looking at a population that is only a sixth of modern day Britain. So we could think of it in terms of the equivalent now of 600 deaths a day, not just in the bad times but average through the year. There was no cure for smallpox and many of the survivors, badly scarred, were much to be pitied. Good nursing care helped to mitigate the severity of the awful disease but most therapies were worse than useless. While there was still no knowledge of microbial infection, there was increasing recognition that the disease was communicated from person to person. Preventive methods of course, social distancing and the like, only delayed the reckoning. Most people who lived to a good age had smallpox at some stage. The children of the urban poor died in great numbers as infants but the children of the closeted rich often died in adolescence. For all the deficits of medical understanding, people were in some respects better placed to manage smallpox than we are at present with COVID-19. There were certainly asymptomatic cases but probably relatively few but crucially, patients were not infected until they had high fever and the telltale spots broke out. At the other end of the cycle, a week or so later, the drying of the smallpox vesicles signalled recovery. Although there was no understanding of the immune system, it was recognised that a smallpox survivor did not succumb to the disease a second time. One immediate advantage of this observation was that survivors could nurse the sick and keep life going. Young people of course not only died from the disease but were badly scarred. They lost their looks but what they lost perhaps in the marriage stakes they gained in the employment stakes. Some jobs required people to have had scars on their face showing that they were immune to smallpox, particularly of course if you were looking for servants in the household or particularly servants in the nursery. Over the centuries, various cultures developed practices in which people deliberately exposed themselves or their children to the infection. There was always some advantage in exposing oneself to smallpox when in health and perhaps when the outbreak was relatively mild. Associating the infection with sympathetic magic or religious rituals may not have been wholly valueless, particularly when it comes to ablutions and so on. By trial and error, it was found that infecting someone by scratching in or inoculating smallpox matter on the outer limbs was more likely to bring about a less severe response. Early in the 18th century, the Royal Society in London received reports of inoculation practices in China and Turkey and in 1717 Mary Worthy Montagu, the wife of the ambassador in Constantinople, had her son inoculated there, or such is modern Istanbul. Back in Britain, she sought to make the practice fashionable while the Royal Society busily gathered data showing that mortality rates in cases of inoculated smallpox were much less than in smallpox acquired naturally. Medical statistics and probabilistic thinking helped the practice establish itself during the Enlightenment, especially in the English-speaking world. Some specialist inoculators, like Daniel Sutton, made inoculation a business, improving outcomes and pushing down costs. For most parents in Britain and elsewhere in the European world though, it remained an awesome risk to take on behalf of one's children. The chance of a child dying, even a chance of one in a hundred or one in several hundred, still seemed too much of a risk for many parents, posing an awful dilemma. It seemed to people that it was tempting providence, and religion and superstition inhibited people from using the practice to the uppermost. Edward Jenner was born in Berkeley in 1746. He was inoculated at his village school in 1753, and he would then have been one of a very small minority of people who went through what was still a highly dangerous and rather brutal procedure. By the late 1760s, smallpox inoculation was being improved and was becoming rather more common. More important, groups of people were often going through inoculation together, making it possible, of course, to observe patterns of the experience of different people, the age and sex and so on and so forth, and also possibly look at factors that helped the process. This broadening of practice reaped great dividends in terms of smallpox management. It provided vital information on the lapse of time between first infection, which of course would always be generally obscure, and the time when symptoms showed. And of course, having that knowledge allows you then to be a little bit preemptive in terms of care, and of course, isolating people who are going to break out in spots. It also provided a very valuable diagnostic tool, making it possible to test whether people were already immune, picking up some people who may have had smallpox asymptomatically, or perhaps they thought they'd had chickenpox, when in fact they'd had a mild case of smallpox and so on. So a very important diagnostic tool. And that, of course, is going to have enormous value when it comes to vaccination. Kiernan himself vaccinated on some scale as a country practitioner operating in Gloucestershire. And in the course of so doing, he found some patients that he could not infect with smallpox. They resisted the inoculation process. Some of them pointed out, or a few of them pointed out, that they thought that they had immunity. They were protected because they'd caught cowpox accidentally. And this, of course, is what Jenner then proceeded to investigate, pursuing his inquiries really over several decades. Cowpox was a rare disease. It was sporadic. And occasionally, of course, he would hear of an outbreak on a local farm. And occasionally he'd meet people in the practice who had some infection. But generally speaking, people didn't go and see a practitioner with a cowpox infection. His inquiries proceeded very slowly because also there was very little definition in what cowpox was. And he found that farmers use the term, of course, to refer to a number of pustular diseases on cows. And he started to realise that only one of these, and he could only tell the difference by observation, was the one that potentially could protect from cowpox. Jenner was a very inquisitive man and also committed very much to experimentation, but he really had no opportunity much to put to the test the notion that cowpox protected from smallpox. He was very reluctant to, even when he found a cow with cowpox, to try to use that cowpox inoculating a human being. What he had in mind was waiting for an opportunity for someone to present themselves with a ripe cowpox pustule on their hand, and then to use that immediately, that humanised cowpox lymph with some patients who came to him for routine smallpox inoculation. And this is what he achieved in 1796 with the son of his gardener, James Phipps, who presumably was putting himself forward for smallpox inoculation, and Jenner said, well, smallpox inoculation is rather more dangerous, but I've got this other idea and it should get a mild response. So it did, and a month later Jenner, of course, tested young Phipps by trying to inoculate him with smallpox and found that he resisted the disease. So this is what Jenner writes up in terms of his experiments. He puts together all the cases he's accumulated of people who've had cowpox in the past and have not had smallpox subsequently, and the tests he's made to ascertain the truth of the matter, and then of course his recent experiments with James Phipps, and in particular then his subsequent experiments where he continues to use cowpox, humanised cowpox, to transferring it from child to child and using, in a sense, a series of successive transmissions of humanised vaccine. He wrote this up in a treatise in 1798 and he set forward, of course, his argument that cowpox should be looked at as a possible substitute for smallpox in inoculation. He argued that it was just as effective as smallpox inoculation, which probably wasn't quite true in the end, but it was obviously a lot safer. No one died from cowpox inoculation. They did die from smallpox inoculation occasionally, and more to the point perhaps, smallpox inoculation was all right for individuals, but smallpox inoculation communicated disease and quite often, of course, smallpox inoculation might provoke a local outbreak. Vaccination attracted a great deal of interest and one of the points that emerged fairly rapidly, and Jenner had been modest about this in his first treatise, but he becomes stronger on it as he gets positive feedback, is that, of course, cowpox inoculation isn't just an improvement of smallpox inoculation, it's something rather different because it in fact could lead to the eradication of smallpox. Smallpox inoculation can save individuals, it can help contain vaccination, but in inoculating smallpox, you're actually giving the disease, you're actually spreading, helping to spread the disease. Well, Jenner's ideas were getting a lot of attention and not just in Britain, but through newspapers, reports, correspondence and so on in Western Europe and across the Atlantic in North America, and in a sense, a global conversation was beginning to develop about the potential of vaccine. Along with the letters, Jenner and other colleagues in London, there'd been a series of major trials in London which had established Jenner's case statistically more effectively. There was a global conversation and a great deal of interest. One of the exciting aspects of this topic really is to find just how well documented it is. There's no one who writes letters or keeps a journal that doesn't mention cowpox at this time. Jane Austen, for example, mentions this in her letters and virtually everyone who was alive at the time found it absolutely fascinating. And at the same time, people wrote up their experiments, they were reported in newspapers, there were book-length expositions and so on and so forth. And one of the interesting things is the way in which, of course, it gives, by looking at the responses of people to the value of cowpox and the promise of vaccination, you get insights into the lives of individuals, family dynamics, their encounters with professional medicine, their religious and cultural values, their levels of trust in government and science. And one of the things that we're finding with COVID-19, I think, is that we're learning quite a lot about ourselves through observing the working of this disease and similarly, I think, in relation to the early development of vaccine. As with the spread of viruses generally, studying, of course, cowpox discloses connectivity in an increasingly globalised world. And what we're looking at, of course, is the rapid spread of cowpox around the world as a preventative of smallpox. In terms of readiness to embrace vaccination and ways in which they try to establish the practice, political, social and cultural contexts were very important, as is becoming very obvious, even though there's a surprising degree of commonality in human responses, conditioned, of course, by longstanding fear of smallpox. After some initial scepticism, most medical men came behind and backed vaccination and were very eager to introduce it in their practices. And that included quite a lot of indigenous practitioners, health workers in different parts of the world, as in India and Siberia and Peru. It was sometimes hard, of course, to persuade parents of the validity of inflicting on their beautiful young children a cattle disease. The idea seemed quite repugnant and there were, of course, concerns in many cultures about bodily purity and contamination and so on. And it's here that we do see a very favourable cultural climate, I think, in the age of Romanticism, which privileged, of course, nature and the natural world and the beneficence of God's creation. And what's interesting is how rapidly we see the promoters of vaccination stressing the wholesomeness and the cleanliness and the beneficence of the cow, how it provides for so many of human needs and so on and so forth, and using those sorts of images to promote and justify the practice. We also see, though, similarly concerns about bestialisation and we do see a sort of anti-vaccination lobby that drums up cases where they argue that vaccination has created bodily deformity and indeed the growth of hair and making animal noises among children and so on and so forth. Gilray's famous caricature is a little bit hard to read. Is he actually setting up, is he anti-vaccination or is he mocking concerns about bestialisation among the people? What we're looking at is a remarkable mobilisation, most obviously mobilisation of medical networks in support of the practice, but a much larger mobilisation as people busily inform themselves and discuss among themselves their response to vaccination. We get many observations and I've just picked out one of many women who write about vaccination, and this is the famous Quaker, Elizabeth Fry, and she confides in a journal, the idea is not pleasant, it almost looks like taking too much on ourselves to give a child a disease. But I altogether felt easy to do it. I read a great deal about the operation, which was very little and easily performed. What a wonderful discovery it is if it really prevents the smallpox. Well, not all people, of course, were quite as careful and discerning as Elizabeth Fry and it also, of course, became quite fashionable. Importantly, of course, the elite got behind the practice, some for fashionable reasons, obviously, but mainly because they saw that it worked, they adopted it in their own families, and then they encouraged its use, often by charitable subscription of new institutes to offer vaccine to the poor. The clergymen get in the act, many clergymen champion vaccination, some parsons try to use the baptism or preparation for baptism as a time to inform parents that this is a licit operation and it will work, and indeed, of course, often vaccinations were organised at parish level. And we get, of course, a lot of bills and handouts and so on and so forth, encouraging the process, explaining what vaccination is, and this, of course, is a French broadsheet doing so. Vaccination spread very rapidly in Western Europe, and while in Britain and North America in particular, it was always very much a matter of private initiative and the medical marketplace developing a solid grounding of vaccination. In Western Europe, governments were much more actively involved, and we see this particularly in France, in Napoleonic France, but also in all the other European states, where generally we've seen traditions of what's sometimes called enlightened absolutism, where governments are much more active in trying to promote change in their communities, and so it is with vaccination. One of the things that people felt in England very much was that in Europe they were doing it rather better. Governments were becoming involved and giving proper support to the vaccination initiatives. Napoleon himself was a great admirer of vaccination, and he put the whole government machine in Napoleonic France and Napoleonic Europe generally into supporting the practice. We can see some of the sense of mobilization when we look at the instructions of the Minister of the Interior, Chaptal, to the prefects in France. He uses strikingly martial terms. He says we need to dispute every inch of ground with the enemy whom we wish to exterminate, the enemy being smallpox, although of course at this time we're in the midst of the Napoleonic Wars, and one of the remarkable things of course is how that sets the tone for mobilization and also encourages even someone like Jenner to start using military metaphors to declare himself at war with smallpox and at war with those opponents of vaccination. He writes to a couple of ladies who lived in Wales and were practicing vaccination. He congratulates them on, quote, opening the vaccine campaign so successfully, and continued, may this species of warfare never terminate till you have driven from your country the most formidable foe that ever invaded it. So again, this is in the context of Britain facing invasion from France and in a sense the military metaphors become loaded and loaded, and in some senses it's the beginning of that process, I think, of talking about war against disease. It's particularly the case, of course, that vaccination needed government support in imperial contexts where there were problems of distance, often there were problems of securing supplies of vaccine and building up the practice, and one of the early achievements of vaccination was to be spread through the Mediterranean and then through the Middle East, through Baghdad to Bombay and then Madras, where the British authorities really strongly supported vaccination. Obviously, in India and Ceylon, Sri Lanka, there was a great need of some assistance with smallpox. The Indians actually in Bengal had a traditional form of inoculation and they were fairly effective, but in most parts of India and in Sri Lanka that practice of inoculation hadn't developed, and Dr James Anderson, who was based at Madras in modern Chennai, was very successful in achieving large-scale vaccination with the assistance of native practitioners, and we see this monument to one of his lieutenants, Soumya Naik, who vaccinated over 700,000 people between 1802 and 1828. He probably has a world record in terms of the people he vaccinated. We also see government being very active in the Russian Empire. Vaccine becomes available in Moscow in 1801. Tsar Alexander makes provision for a vaccine expedition through the provinces of the Russian Empire. This sets out in 1802 and it really only gets through the provinces west of the Urals, but there was a vaccination unit linked to a great embassy that was sent to China through Siberia in 1805, and vaccination was extended in that fashion. Here we see a watercolour actually done by a Russian physician of vaccination among the Buraats near Irkutsk over the winter of 1805-6. In Russia, of course, illiteracy was a major problem, but they had a tradition of woodcuts, informative woodcuts, and we see a whole series of them promoting vaccination. And then we see the Spanish Royal and Philanthropic Vaccine Expedition. One of the big problems with vaccine was how to preserve it and transmit it over space and time. One of the interesting points is that really cowpox was only found in England. That's not strictly true, but very largely all the vaccine that we're looking at in the early years of the 19th century originates in England. And of course, they don't originate entirely in dairy farms. What we're looking at is the way in which Jenner himself, of course, had vaccinated people, then used from the vaccine pustule lymph to vaccinate the next batch of people. And so what we get, of course, is that then some of that vaccine is preserved, it's dried, it can be sent off in the post to friends, and it can be then used in future practice. The problem is it doesn't survive all that well, but we're seeing how vaccination is necessary for the production of vaccine. And when in Napoleonic France, for example, Napoleon orders people to establish vaccine committees in every department, the idea is that that committee will organise vaccination and maintain a vaccine depot. And they do so generally by organising something in the orphanage so that they can regularly be vaccinating two or three orphans a week and generating a supply of lymph that then becomes more widely available. And all the practitioners have a practice of, of course, calling their patients back and checking that the vesicles, whether the vaccination has taken place. And of course, what they're also doing is taking lymph to use on the next set of patients. And this is one of the reasons why right away that the vaccine clinics vaccine two times a week, usually Tuesday and Friday. And this means that 10 days later, the group from the previous Tuesday will be coming on the Thursday. They will be then used to vaccine the next group and so on and so forth. And this is the way the system developed. How to get the vaccine around the world, particularly through the tropics and over long voyages? Well, they use the same procedure and we see this being developed on a grand scale by the King of Spain to get vaccine to Spanish America and then to the Philippines. Essentially, 22 orphans are recruited and they are vaccinated in pairs successively so that you vaccinate two of them. Eight days later, they'll be a postul, you vaccinate the next two and so on and so forth. And by that stage, you can be in Tenerife and then in Puerto Rico. You'd then be recruiting other boys and so on and so forth. So this is how vaccination was spread around the Spanish empire in what was really a magnificent, what's called philanthropic vaccine expedition. It took it to eventually across to the Philippines, to Macau and then to Canton. So this is where we see really the encirclement of the world by vaccine. Alexander Pearson, the surgeon of the East India Company at Canton, prepared a text that was then translated and published in Chinese. And he had also a clear notion that the practice would only develop insofar as Chinese took it up themselves, or Chinese practitioners took it up themselves. And some of them did and vaccinated very successfully. And then a reference from Marceau Delano, who was a whaler operating out of Massachusetts, arrives in the Pearl River, and he too finds the first time vaccine is available. And he has some natives from Hawaii on board ship, and he has them all inoculated with it. Well, what we're looking at, I think, is a sort of revolution. And I think that in many ways, we can say that in this age of revolutions, there was a significant vaccination revolution. The momentum was coming to an end really by about 1815. But nonetheless, the practice was well established in most parts of the world. And you can see, of course, some of the difference that it had made both, perhaps at a very private level in the journal of Lady Maria Nugent, who's the wife of the governor of Jamaica. Her son is born in November 1802. She's very anxious about him. She writes in a journal, my dear boy is prospering, but alas, we must soon think of giving him the smallpox, that is inoculating him. And then a year later, her daughter arrives, and vaccine is available. We agreed to have the puncture made in her dear little leg, for if the present fashion for excessive short sleeves lasts till she grows up, it will not be becoming to expose a scar, which I now see disfiguring many pretty young ladies. And then from John Herschel, we get an acknowledgement of the awesome scientific development, whereby one of the most frightful scourges of the human race is being extirpated in many parts of the world. Happily for us, we know only by tradition, the ravages of the smallpox, as it existed amongst us hardly more than a century ago. And as it would, in a few years, infallibly exist again, were the barriers which this practice opposed to its progress be abandoned. And we must finally, of course, acknowledge Jenner's own genius, because in some ways he had no understanding of modern virology and immunology. Most people in that field still recognise that he sort of sensed what was necessary to do. And when Louis Pasteur made the next move in terms of developing a vaccine, he decided to use vaccination as a generic term for all prophylaxis, prophylactic measures in relation to all diseases. And that is why we're still waiting for a vaccine for COVID-19. Great, thanks. Thanks very much for that, Michael. That was really good. So yes, just to let the audience know, obviously they can submit questions to the chat box. We've had just a couple so far, so I'll just read those out to you. So there's one question about whether slaves perhaps were forcibly vaccinated, whether you could say something about how vaccination was spread to slave owners and slave populations. Slave populations were very significant in terms of early inoculation, the older practice. Some slaves, of course, knew all about forms of scratching smallpox. So there were indigenous African traditions that made it quite familiar. Many slaves, I think, were inoculated before the Middle Passage, as inoculation got developed in Britain and France. There is some sense in which the records don't make it always clear whether slaves were forcibly inoculated. In many cases, they would have been, but in some cases, certainly they weren't. That is, there was a sense that this was something that they had some control over. When it came to vaccination, we're in a rather different space, of course. This is a time when certainly vaccination was regarded as quite important and of benefit to people generally. One sees, for example, some slave owners offering it to their population. We see in places like Cuba, slaves being routinely vaccinated when they arrived in Havana. This is after the British abolition of the slave trade, of course. And, of course, being very important in terms of supplying vaccine to the whole colony, because there you've got continually people being processed and so on. Convicts weren't vaccinated forcibly. In Britain, for example, some paupers were sometimes told that they wouldn't be on the parish unless they agreed to vaccination. So they were threatened, if you like, with their livelihood. But this is only mentioned in contexts where people thought that that was a very wrong thing to do. So, yes, the context of slavery is very important, both in terms of developing understandings of inoculation and then also vaccination to some degree, but also in the way in which slaves were actually treated and the situations they found themselves in. Great. OK, but another question here says, could you say something about the religious resistance to vaccination? There were a lot of concerns with smallpox inoculation, of course, and because the line that the major religious traditions in Christianity and Judaism in particular had it, of course, was that if, in fact, it was on medical advice, if it was a good idea to do it medically, then the church wouldn't oppose it. But many people did feel that smallpox inoculation involved such great risk that it was wrong to adopt the procedure. It's tempting providence. In respect of vaccination, all the mainstream churches became very supportive of vaccination. There were smaller groups of more fundamentalist Calvinists, for example, who didn't quite approve of vaccination. There was a perception that in the Islamic world there wasn't much prospect of vaccination being taken up. It was believed that the Muslims were fatalistic in not allowing that sort of intervention. The pattern, though, is rather complex because one of the things is that originally smallpox inoculation in Turkey was largely the preserve of Christians and Jews rather than Muslims. But some Muslim rulers were interested and some Arabs, for example, have their own traditions of inoculation. In India, quite a lot of the Muslims seem to have responded well to vaccination. Hindus, again, had a rather different set of issues in relation to vaccination. There was some hope that the source of cowpox being the holy cow might make the Hindus responsive to the new procedure. But, of course, it didn't work that way and many Hindus didn't like the procedure. But we certainly do find quite a lot of them do take it up and many Indian princes and so on championed vaccination in the early 19th century. It becomes rather more divisive actually in the later 19th century. It becomes much more an issue, vaccination, in terms of colonial conflict and so on in the late 19th century. Great, thank you. So we have another question that's sort of slightly related to what you just said. Obviously, even after vaccination was sort of spreading around the world, but we know that it did take another couple of hundred years for it to actually be eradicated. So did something go wrong with that or what was the kind of causes of it not being as effective more immediately? This is something that obviously I'm very interested in. What was it that went wrong? Because what you have got, of course, in the early 19th century, very rapid take up, millions of people and, in fact, quite good strides made in terms of really containing, if not eradicating, the disease in parts of Europe. It falls apart because really of the problem of apathy and the fact that most people want to delay vaccination until they think there's a real danger. And so the very success of vaccination in the 1810s, 20s, to some extent, meant that people sat back and didn't bother vaccinating and supplies of vaccine ran out. Sometimes then there'd be an outbreak and there wouldn't be enough vaccine and so on. But the other sort of double whammy here was that, and this is something that Jenner didn't realise until rather late in the piece, was that vaccination itself wasn't for life. And so there were some doubts about vaccination when a fair number of people who thought they'd been vaccinated properly still got smallpox. They were actually helped by their prior vaccination, but they really needed to have a second vaccination to strengthen it. So after eight or 10 years, there were problems of people with smallpox after vaccination and people then saying, well, smallpox inoculation at least gave them security. But the other thing that people weren't aware of was how people's immune systems are topped up by exposure to smallpox. So if there's smallpox around and you've been vaccinated for smallpox, then in fact your immunity is actually being topped up by someone next door having smallpox and so on. And as soon as, of course, smallpox disappears to a significant degree, then again, when it comes back, there's less resistance. So these are the sorts of problems that came through. And some, of course, moved to a compulsory vaccination and that set up all sorts of other controversies and a stronger anti-vaccine movement. Some European countries managed it better than England, where there was great hostility to compulsory vaccination when it finally came in in the 1850s. The truth of the matter is, though, of course, smallpox was very largely contained in most parts of Europe and North America. And although there were outbreaks, people were able to bring them rapidly under control. And of course, the larger problem was then really the rest of the world, whether there were the resources and the will to manage that. And that didn't happen until after the Second World War, with the WHO's backing of a systematic campaign of eradication.