In the history of the United States, smallpox played a pivotal role in shaping the direction of the country's development. When Europeans first arrived in the Americas, they unintentionally introduced smallpox to the continent and the disease helped to wipe out as much as 95 percent of indigenous Americans. This was one factor that allowed European settlers to colonize the continent with relative ease, although the disease remained active in the Americas until the second half of the twentieth century. The number of smallpox cases in the United States fluctuated between 1900 and 1930, with as many as 110,000 reported cases in 1920, however the number of cases fell sharply in the 1930s, and there were no cases at all in the United States from 1950 onwards. In 1980, the World Health Organization declared the disease to be successfully eradicated on a global scale, making it the first infectious disease to be wiped out by intentional human activity.

Although vaccination was discovered in England in 1796, the practice was not made compulsory until 1853 in England and Wales, and 1864 in Scotland. For this reason, the number of smallpox deaths per million people fluctuated from year to year, often doubling or tripling from one year to the next, before the death rate for both countries settled in the late 1960s. The Great Pandemic of the 1870s, which was the last major smallpox pandemic in Europe, caused the number of smallpox deaths to soar once more, peaking at over 1,000 deaths per million people in England and Wales in 1871, and at over 820 deaths per million people in Scotland in 1872. During this pandemic, mandatory vaccination became enforced, where parents who did not vaccinate their children within the first three years of life were penalized with fines or imprisonment, and this helped the smallpox death rate to remain low and plateau in the final two decades of the nineteenth century; an estimated 11,000 of these penalties were handed out during the 1880s, which included 115 prison sentences for failure to vaccinate children. Smallpox cases in Britain were rare throughout the early twentieth century; not counting a lab accident in 1978 that infected two people (one of whom died), natural smallpox cases were eradicated in Britain in 1934.

In the eighteenth century, before vaccination was introduced to Sweden, smallpox epidemics were much more severe and regular than in the nineteenth century. Between 1774 and 1802, epidemics in Sweden peaked roughly every five years, with the toll reaching over seven thousand deaths per million people in some years. When vaccination was introduced to Sweden in the early 1800s, it greatly decreased the total number of smallpox deaths per million people, with the number never exceeding one thousand deaths per million people in any year after 1809. In actual numbers, there were roughly two thousand smallpox deaths per year in Sweden during the pre-vaccination era; optional vaccination helped bring this average down to 623 deaths between 1802 and 1811, while the number dropped to 176 between 1857 and 1866 when compulsory vaccination was introduced. Vaccination in Sweden became enforced in 1880, where parents were punished with fines or imprisonment for failing to immunize their child, and this helped bring the average number of smallpox deaths to just two deaths per year over the next two decades. Although there were some cases and fatalities recorded in the late 1890s, naturally occurring cases of smallpox were eliminated in Sweden in 1895, which made Sweden the second country in the world (after Iceland in 1872) to successfully eradicate the disease.

The Great Smallpox Pandemic of 1870 to 1875 was the last major smallpox epidemic to reach pandemic level across Europe. The outbreak has its origins in the Franco-Prussian War of 1870 to 1871, where unvaccinated French prisoners of war infected the German civilian population, before the virus then spread to all corners of Europe. The death rates peaked in different years for individual countries; with the highest numbers recorded in 1871 for the German states, Belgium and the Netherlands, while death rates peaked in Austria, Scotland and Sweden in later years (the states that peaked in 1871 were closer in proximity to the frontlines of the Franco-Prussian War). Impact of compulsory vaccination The average number of deaths per million people was much higher in countries without compulsory vaccination, ranging from 953 to 1,360 in the samples given here. In comparison to this, the countries with compulsory vaccination barely reached these numbers in the years when the epidemic was at its worst, and their annual averages ranged between 314 and 361 deaths per million people during the six years shown here. Impact of the Great Pandemic Following the surge in smallpox deaths caused by the pandemic, many of the countries listed here introduced mandatory vaccination, or introduced penalties for parents who did not vaccinate their children. Germany and the Netherlands** did this in 1874, while Britain and Sweden enforced their vaccination laws with stricter penalties in 1871 and 1880 respectively. Perhaps surprisingly, Austria and Belgium, the two countries with the highest average death rate shown here, never introduced mandatory smallpox vaccination.

The story of smallpox in Stuttgart is a clear example of how vaccination can make a significant impact. In the first 25 years shown here, the number of smallpox deaths averaged at 224 deaths per year, before a slight increase over the next five years to 274 deaths per annum. With the introduction of vaccination practices to Europe at the turn of the nineteenth century, a clear decrease can be observed in the next decade, dropping to 154 deaths per year between 1802 and 1806, and falling again to just two deaths per year between 1801 and 1811. In two of the next three five-year periods, the average number of smallpox deaths per year was zero. The state of Württemberg (of which Stuttgart was the capital) was one of the first in Europe to make vaccination compulsory, doing so in 1818; joining its south-German neighbors of Bavaria and Baden at the forefront of the fight to eradicate smallpox.

The World Health Organization (WHO) estimates that there were millions of smallpox cases every year until the 1970s, when the WHO's eradication program then successfully eliminated the disease in nature. Some academic estimates place smallpox's death toll at 300 million in the twentieth century, and 500 million in its final hundred years of existence. The development of the smallpox vaccination, which was the first successfully developed vaccine (the word vaccination comes from the Latin word for cow;"vacca", as cowpox was used to develop the smallpox vaccine), greatly contributed to the significant decline in infant and child mortality across the globe, and the boom in population growth during the twentieth century. Reported cases In spite of these large numbers, the figures for reported cases was only a tiny fraction of this; for example, the WHO estimates that there were fifty million cases in 1950, however less than one percent of these cases were recorded. In spite of this, the data is still useful for showing how smallpox developed and spread throughout the world; we know that the majority of these cases were recorded in the Indian sub-continent, and that epidemics across Asia drove the number of recorded cases up in the middle of the century. The final naturally-occurring cases were observed in 1977, while the two cases in 1978 were due to a lab accident in England, which resulted in one fatality.

The development of vaccination by Edward Jenner in 1796 is seen by many as one of the most important and world-changing medical discoveries ever made. Throughout human history, smallpox was responsible for an untold and innumerable share of fatalities, with epidemics devastating countries (and even continents) in their wake; as of 1980, the World Health Organization declared smallpox to be eliminated in nature, making it the only human disease to have been successfully eradicated. If we look at the share of smallpox deaths in England over the nineteenth century, we can see the impact that vaccination had on society during this time. Decline in Britain Within this century, the number of people dying annually from smallpox dropped from 3,000 per million people in the 1700s, to just ten people per million in the 1890s (it is also worth noting that a smallpox pandemic swept across Britain between 1891 and 1893, which caused this number to be higher than it could have been). Mandatory vaccination was not introduced in England until 1853, but by this point the number of smallpox deaths per million people had already fallen to a fraction of its eighteenth century level, and compulsory vaccination reduced these numbers even further.

Project Tycho datasets contain case counts for reported disease conditions for countries around the world. The Project Tycho data curation team extracts these case counts from various reputable sources, typically from national or international health authorities, such as the US Centers for Disease Control or the World Health Organization. These original data sources include both open- and restricted-access sources. For restricted-access sources, the Project Tycho team has obtained permission for redistribution from data contributors. All datasets contain case count data that are identical to counts published in the original source and no counts have been modified in any way by the Project Tycho team. The Project Tycho team has pre-processed datasets by adding new variables, such as standard disease and location identifiers, that improve data interpretabilty. We also formatted the data into a standard data format.

Each Project Tycho dataset contains case counts for a specific condition (e.g. measles) and for a specific country (e.g. The United States). Case counts are reported per time interval. In addition to case counts, datsets include information about these counts (attributes), such as the location, age group, subpopulation, diagnostic certainty, place of aquisition, and the source from which we extracted case counts. One dataset can include many series of case count time intervals, such as "US measles cases as reported by CDC", or "US measles cases reported by WHO", or "US measles cases that originated abroad", etc.

Depending on the intended use of a dataset, we recommend a few data processing steps before analysis:

• Analyze missing data: Project Tycho datasets do not inlcude time intervals for which no case count was reported (for many datasets, time series of case counts are incomplete, due to incompleteness of source documents) and users will need to add time intervals for which no count value is available. Project Tycho datasets do include time intervals for which a case count value of zero was reported.
• Separate cumulative from non-cumulative time interval series. Case count time series in Project Tycho datasets can be "cumulative" or "fixed-intervals". Cumulative case count time series consist of overlapping case count intervals starting on the same date, but ending on different dates. For example, each interval in a cumulative count time series can start on January 1st, but end on January 7th, 14th, 21st, etc. It is common practice among public health agencies to report cases for cumulative time intervals. Case count series with fixed time intervals consist of mutually exxclusive time intervals that all start and end on different dates and all have identical length (day, week, month, year). Given the different nature of these two types of case count data, we indicated this with an attribute for each count value, named "PartOfCumulativeCountSeries".

Depending on the reach and level of vaccination within Europe's various states in the 1870s, smallpox had a varied impact on various age groups. For infants below the age of one year, smallpox was responsible for between 15 and 30 percent of all deaths in the given regions, as many of these babies had not yet been vaccinated and were at a high risk of succumbing to the virus. In states where the vaccination of infants was not compulsory, such as the Netherlands, Berlin (Prussia) and Leipzig (Saxony), the share of deaths due to smallpox among young children remained high, while it was relatively low in Hesse and Scotland, who had introduced mandatory vaccination in 1815 and 1864 respectively. Great Pandemic highlights the need for revaccination As Hesse had been vaccinating on a large scale for generations, the share of smallpox deaths was relatively low among young people; however, between 1870 and 1872, over half of all deaths among those aged 30 to 60 years were due to smallpox. The reason for this was because smallpox vaccination in infancy did not guarantee lifelong protection, therefore immunity often wore off in adulthood. In the 1830s and 1840s, several German armies started to vaccinate new recruits regardless of whether they had been vaccinated in infancy or not; when scientists compared the smallpox death rates in the army with that of the civilian population during this pandemic, they noticed that it was much lower in the army, due to these revaccination policies. This discovery helped many scientists in Europe recognize the need for revaccination, which greatly contributed to the eradication of the disease across most of Europe in the early twentieth century.

Vaccination has been critical to the decline in infectious disease prevalence in recent centuries. Nonetheless, vaccine refusal has increased in recent years, with complacency associated with reductions in disease prevalence highlighted as an important contributor. We exploit a natural experiment in Glasgow at the beginning of the 20th century to investigate whether prior local experience of an infectious disease matters for vaccination decisions. Our study is based on smallpox surveillance data and administrative records of parental refusal to vaccinate their infants. We analyse variation between administrative units of Glasgow in cases and deaths from smallpox during two epidemics over the period 1900–1904, and vaccine refusal following its legalisation in Scotland in 1907 after a long period of compulsory vaccination. We find that lower local disease incidence and mortality during the epidemics were associated with higher rates of subsequent vaccine refusal. This finding indicates that complacency influenced vaccination decisions in periods of higher infectious disease risk, responding to local prior experience of the relevant disease, and has not emerged solely in the context of the generally low levels of infectious disease risk of recent decades. These results suggest that vaccine delivery strategies may benefit from information on local variation in incidence.

From the 1630s to the 1830s, the annual number of smallpox deaths in each decade fluctuated greatly in London. The population of London in 1650 is estimated to have stood at 350,000 inhabitants, with an average annual death toll of roughly 680 people during this time. As London's population grew over the next hundred years, the number of smallpox deaths also increased at varying rates in each decade. Scientific advancements flatten the curve The average number of annual smallpox deaths was between 1.7 and 2.5 thousand in each decade between 1710 and 1799, as the introduction of inoculation (i.e. using a mild dose of smallpox to develop some immunity to the virus) helped to lower the smallpox death rate to some extent. Following Jenner's discovery of vaccination in 1796 (which provided a much safer and more reliable method of protection), the death rate decreases further. London's population at this time was just under one million people, and the average number of deaths in the first decade of the 1800s was 1.4 thousand per year (or 1.4 deaths per thousand inhabitants). Vaccination brought this number down even further in the next quarter century, despite the fact that mandatory vaccination was not implemented by the British government until 1853. Smallpox death rate in other capitals While there is little reliable data for other major cities in the seventeenth or early-eighteenth century, London's death rate can be compared with that of Berlin or Copenhagen at the turn of the nineteenth century, during a time of increased urbanization and industrialization. In 1800, Berlin was estimated to have a population of roughly 170,000 people, and Copenhagen's was 100,000. This gave Berlin a smallpox of death rate of roughly 2.7 deaths per thousand in the first decade of the 1800s, and Copenhagen's was 0.67 deaths per thousand. Berlin's smallpox death rate was consistent between 1770 and 1809, while Copenhagen and London's both decrease after vaccination was introduced (Denmark made it mandatory in 1810). Unfortunately, a lack of information from this time makes it difficult to draw further conclusions about the spread of smallpox in urban centers in these years.

Following Edward Jenner's development of the smallpox vaccine in 1796, the death rate due to smallpox in England and Wales dropped significantly. Although Jenner's work was published in 1797, it would take over half a century for the British government to make vaccination compulsory for all infants. Between 1847 and 1853, when vaccination was optional, children under the age of five years had, by far, the largest number of deaths; the total death rate was 1.6 thousand deaths per million people, which was more than five times the overall death rate due to smallpox. When compulsory vaccination was introduced, this helped bring the smallpox death rate in this age group down by over fifty percent between 1854 and 1871. When compulsory vaccination was enforced with penalties in the wake of the Great Pandemic of the 1870s, the smallpox death rate among children under the age of five dropped to approximately fifteen percent of its optional vaccination level. Increase among adults Along with the youngest age group, children aged five to ten years also saw their death rates decrease by roughly two thirds, and the death rate among those aged ten to 15 declined by just under one third during this time. It was among adults, aged above 15 years, where the introduction of mandatory vaccination had an adverse effect on their death rates; increasing by fifty percent among young adults, and almost doubling among those aged 25 to 45. The reason for this was because, contrary to Jenner's theory, vaccination did not guarantee lifelong protection, and immunization gradually wore off making vaccinated people susceptible to the virus again in adulthood. There was some decline in the smallpox death rates among adults throughout the 1870s and 1880s, as revaccination became more common, and the enforced vaccination of children prevented smallpox from spreading as rapidly as in the pre-vaccination era. Overall trends While the introduction of mandatory vaccination saw the number of smallpox deaths increase for age groups above 15 years, the overall rate among all ages decreased, due to the huge drop in deaths among infants and children. The smallpox death rate dropped by over one quarter when compulsory vaccination was introduced, and it then fell to just over one third of it's optional-vaccination level when these measures were enforced. The development of the smallpox vaccine and the implementation of mandatory vaccination led to the eradication of the disease in Britain by 1934, and contributed greatly to the demographic developments of the twentieth century, such as the declines in fertility rate and birth rate, and the increase in life expectancy.

In Britain in the early 1890s, a smallpox epidemic spread across the country and infected thousands. While the death rate was just a fraction of the level observed during the Great Pandemic of the 1870s, the overall death rate increased from 16 deaths in 1890 to 1,456 deaths in 1893. Among all outbreaks shown here, there were more cases among those who were vaccinated and over the age of ten than in any other group, however the death rate of the infected ranged from just one to ten percent. To put this into context, the death rates among the unvaccinated over the age of ten reached as high as forty percent in Gloucester. Unvaccinated children below ten years of age had the highest death rate among infected cases, and in the second outbreak in London, there were 148 deaths in 205 cases among unvaccinated children, whereas there were no deaths in 72 cases among vaccinated children. Another development in this pandemic was that the number of cases in children below the age of ten years was much lower than those above the age of ten; this trend that did not exist in previous centuries. A century of change In the pre-vaccination era, smallpox cases among adults were rare, as the majority of adults had contracted smallpox as children and had therefore built up a tolerance to the disease. In the early nineteenth century, the number of cases among children decreased, thanks to the protection granted to them through vaccination; however vaccination did not guarantee lifelong protection, which meant that the share of smallpox cases in young adults rose until revaccination then brought this trend back down. As we can see during these epidemics in England in the 1890s, the distribution of smallpox cases was much more representative of the population's age distribution, showing the impact and development of vaccination in its first century.

Project Tycho data include counts of infectious disease cases or deaths per time interval. A count is equivalent to a data point. Project Tycho level 1 data include data counts that have been standardized for a specific, published, analysis. Standardization of level 1 data included representing various types of data counts into a common format and excluding data counts that are not required for the intended analysis. In addition, external data such as population data may have been integrated with disease data to derive rates or for other applications.

Version 1.0.0 of level 1 data includes counts at the state level for smallpox, polio, measles, mumps, rubella, hepatitis A, and whooping cough and at the city level for diphtheria. The time period of data varies per disease somewhere between 1916 and 2011. This version includes cases as well as incidence rates per 100,000 population based on historical population estimates. These data have been used by investigators at the University of Pittsburgh to estimate the impact of vaccination programs in the United States, published in the New England Journal of Medicine: http://www.nejm.org/doi/full/10.1056/NEJMms1215400. See this paper for additional methods and detail about the origin of level 1 version 1.0.0 data.

Level 1 version 1.0.0 data is represented in a CSV file with 7 columns:

• epi_week: a six digit number that represents the year and epidemiological week for which disease cases or deaths were reported (yyyyww)
• state: the two digit postal code state abbreviation that represents the state for which a count has been reported
• loc: the name of a state or city for which a count has been reported, capitalized
• loc_type: the type of location (STATE or CITY) for which a count has been reported
• disease: the disease for which a count has been reported: HEPATITIS A, MEASLES, MUMPS, PERTUSSIS, POLIO, RUBELLA, SMALLPOX, or DIPHTHERIA
• cases: the number of cases reported for the specified disease, epidemiological week, and location
• incidence_per_100000: the number of cases per 100,000 people, computed using historical population counts for cities and states as reported by the US Census Bureau

Project Tycho data include counts of infectious disease cases or deaths per time interval. A count is equivalent to a data point.

Project Tycho level 2 version 1.1.0 data include data counts that have been filtered from the raw data to render standardized data that can be used immediately for analysis. All level 2 data were originally reported in a consistent format and have not been transformed into a standard format by Project Tycho staff, except for smallpox records that included repeated counts for the same location and week, but sometimes with different numbers. These duplicate smallpox records have been averaged into one count for each location and week. Level 2 data include counts for a wide variety of diseases and locations for varying time periods. Because we removed data in an inconsistent format from level 2 data, counts may be missing for certain diseases, locations, or years. For the most complete collection of standardized data, we encourage users to use Project Tycho version 2.0 datasets.

More detailed methods and additional information about the origin of Projec Tycho level 2 version 1.1.0 data can be found in our original publication in the New England Journal of Medicine: http://www.nejm.org/doi/full/10.1056/NEJMms1215400

Level 2 version 1.1.0 data is represented in a CSV file with 11 columns:

• epi_week: a six digit number that represents the year and epidemiological week for which disease cases or deaths were reported (yyyyww)
• country: a two digit country abbreviation, only including "US" in version 1.1.0
• state: the two digit postal code state abbreviation that represents the state for which a count has been reported
• loc: the name of a state or city for which a count has been reported, capitalized
• loc_type: the type of location (STATE or CITY) for which a count has been reported
• disease: the disease for which a count has been reported, in all capitals
• event: an indicator representing the disease outcome reported, including "CASES" or "DEATHS"
• number: the reported number of cases or deaths
• from_date: the start date of the time interval for which a count was reported, as yyyy-mm-dd
• to_date: the end date of the time interval for which a count was reported, as yyyy-mm-dd
• url: the URL of the source document from which the count was obtained

In nineteenth century Belgium, smallpox vaccination was available but was never made compulsory. For this reason, the number of deaths due to smallpox fluctuated regularly (although data before 1864 is scarce*), and the Great Pandemic of the 1870s caused the number of smallpox deaths in Belgium to skyrocket to 4.2 thousand per million people in 1871. Several sources suggest that smallpox had a similar impact in the Netherlands throughout the early and mid-1800s, however the Netherlands introduced mandatory vaccination for all children who were to be enrolled in school in 1873, and following the Great Pandemic the Netherlands' death rate was much lower than that of Belgium. The last natural case of smallpox was recorded in the Netherlands in 1900 (making it the fourth country in the world to eradicate the disease on a national level), while the last endemic case of smallpox in Belgium occurred in 1926. Data for Italy and Hungary is also scarce throughout the century, however Hungary introduced mandatory vaccination and revaccination in 1887, while Italy did the same in 1888; over the next decade we can see that the average number of smallpox deaths in these countries decreased greatly, and endemic cases of smallpox were eliminated in Hungary in 1923, and in 1947 in Italy.

Before Jenner's work made vaccination commonplace at the turn of the nineteenth century, smallpox disproportionately affected children more than adults, with the share of deaths among those aged below ten years typically above ninety percent. This number even reached one hundred percent in some epidemics, such as in Chester, England in 1775; where all 202 smallpox deaths that year occurred in children below the age of ten, and 180 of these were in children below the age of five. Following the introduction of vaccination practices, which generally had the highest rates across Britain, Germany and Scandinavia, the share of smallpox cases in those aged above and below ten years saw a significant decrease, falling as low as 3.65 percent in one sample in London in 1822. The study in Marseilles is the only case shown here where the distribution of smallpox deaths was close to the figures shown in pre-vaccination Europe; this may be due to the political instability caused by Bourbon rule in post-Napoleonic France, as French authorities typically did not promote or enforce vaccination; a factor that would contribute greatly to the outbreak of the Great Smallpox Pandemic of the 1870s.

The 3.5-million-word Victorian Anti-Vaccination Discourse Corpus (hereon VicVaDis) is intended to provide a (freely accessible) historical resource for the investigation of the earliest public concerns and arguments against vaccination in England, which revolved around compulsory vaccination against smallpox in the second half of the 19th century. It consists of 133 anti-vaccination pamphlets and publications gathered from 1854 to 1906, a span of 53 years that loosely coincides with the Victorian era (1837-1901). This timeframe was chosen to capture the period between the 1853 Vaccination Act, which made smallpox vaccination for babies compulsory, and the 1907 Act which effectively ended the mandatory nature of vaccination.

The Quo VaDis project applies the latest techniques for large-scale computer-aided linguistic analysis to discussions about vaccinations in public discourse, and specifically in: social media discussions in English, UK Parliamentary debates and UK national press reports. The goal is to arrive at a better understanding of pro- and anti-vaccination views, as well as undecided views, which will inform future public health campaigns.

The project will be based in the world-renowned ESRC Centre for Corpus Approaches to Social Science (CASS) at Lancaster University, which was awarded a Queen's Anniversary Prize for Higher and Further Education in 2015. An interdisciplinary project team will work in interaction with three main project partners: Public Health England, the Department of Health and Social Care and the Department for Digital, Culture, Media & Sport.

The World Health Organization's (WHO) list of top ten global health threats includes 'vaccine hesitancy' - 'a delay in acceptance or refusal of vaccines despite availability of vaccination services'. Vaccination programmes are currently estimated to prevent between 2 and 3 million deaths a year worldwide. However, uptake of vaccinations in 90% of countries has been reported to be affected by vaccine hesitancy. In England, coverage for all routine childhood vaccinations is in decline, resulting in the resurgence of communicable diseases that had previously been eradicated. In August 2019, the UK lost its WHO measles elimination status.

The reasons for vaccine hesitancy are complex, but they need to be understood in order to be addressed effectively. This project focuses on discourse because the ways in which controversial topics such as vaccinations are talked about both reflect and shape beliefs and attitudes, which may in turn influence behaviour. More specifically, vaccinations have been the topic of UK parliamentary debates since before the first Vaccination Act of 1840; they have been increasingly discussed in the UK press since the early 1990s; and anti-vaccination views in particular have been described as part of a complex network of 'anti-public discourses' which, in recent years, are known to be both spread and contested on social media.

This project will involve the analysis of three multi-million-word datasets: (1) English-language contributions to three social media platforms: Mumsnet, Reddit and Twitter since the inception of each platform - respectively, 2000, 2005 and 2006; (2) UK national newspapers since 1990; and (3) UK parliamentary debates since 1830. These datasets will be analysed in a data-driven fashion by means of the computer-aided methods associated with Corpus Linguistics - a branch of Linguistics that involves the construction of large digital collections of naturally-occurring texts (known as 'corpora') and their analysis through tailor-made software. A corpus linguistic approach makes it possible to combine in a principled way the quantitative analysis of corpora containing millions of words with the qualitative analysis of individual texts, patterns and interactions. In this way, we will identify and investigate the different ways in which views about vaccinations are expressed in our data, for example, through patterns in choices of vocabulary, pronouns, negation, evaluation, metaphors, narratives, sources of evidence, and argumentation. We will reveal both differences and similarities in pro- and anti-vaccination views over time and across different groups of people, particularly as they form and interact on social media.

Our findings will make a major contribution to an understanding of views about vaccinations both in the UK (via our parliamentary and news datasets) and internationally (via our social media datasets). Through the involvement of our Project Partners, as well as more general engagement activities, these findings will be used as evidence for the design of future public health campaigns about vaccinations.

Routine childhood vaccination is important to protect our children against ill health. Vaccines prevent up to 3 million deaths worldwide every year. After clean water, vaccination is the most effective public health intervention in the world for saving lives and promoting good health.Since vaccines were introduced in the UK, diseases like smallpox, polio and tetanus that used to kill or disable millions of people are either gone or seen very rarely. Other diseases like measles and diphtheria have been reduced by up to 99.9% since their vaccines were introduced. Vaccination is not compulsory, however, if people stop having vaccines, it's possible for infectious diseases to quickly spread again. The overall aim of the UK’s routine childhood immunisation schedule is to provide protection against the following vaccine-preventable infections:

A simple susceptible–infectious–removed epidemic model for smallpox, with birth and death rates based on historical data, produces oscillatory dynamics with remarkably accurate periodicity. Stochastic population data cause oscillations to be sustained rather than damped, and data analysis regarding the oscillations provides insights into the same set of population data. Notably, oscillations arise naturally from the model, instead of from a periodic forcing term or other exogenous mechanism that guarantees oscillation: the model has no such mechanism. These emergent natural oscillations display appropriate periodicity for smallpox, even when the model is applied to different locations and populations. The model and datasets, in turn, offer new observations about disease dynamics and solution trajectories. These results call for renewed attention to relatively simple models, in combination with datasets from real outbreaks.