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Number of countries where smallpox was eradicated in nature 1872-1977
Sweden and England. As vaccination practices spread, the severity and frequency of smallpox pandemics declined, and the disease ceased to be endemic in some regions.
For these reasons, Iceland (although a dominion of Denmark at the time) became the first country in the world to introduce mandatory vaccination, in 1802. The Great Smallpox Pandemic of the 1870s was the last outbreak of the disease to reach pandemic level across Europe. Unbeknownst at the time, this would mark the last ever recorded case of naturally occurring smallpox in Iceland, in 1872. This made Iceland the first country in the world to eradicate the disease on a national level; the same factors that had allowed smallpox to be so devastating to Iceland's population in the past (i.e. distance from mainland Europe and a highly concentrated population) had become the reason why vaccination was so effective in the nineteenth century.
Edward Jenner's work on smallpox, published in 1797, was the first time that any scientific findings about vaccination were presented to the wider medical community. Within a few short years of this publication, vaccination had been practiced in most European countries, and the impact was beginning to show almost immediately; particularly in countries such as Iceland leads the way
Epidemics had played a significant role in Iceland's history and development throughout the pre-vaccination era. The country's geographical location meant that viruses did not spread from other countries as frequently as they did on Europe's mainland, however, this also meant that generations would reach adulthood without developing any immunity to these diseases. When these factors were coupled with Iceland's highly concentrated population, this enabled epidemics to spread rapidly throughout the population with devastating effect. The most famous of these epidemics was between 1707 and 1709, where a ship from mainland Europe brought smallpox to Iceland, and the resulting outbreak killed over one third of the entire population.For these reasons, Iceland (although a dominion of Denmark at the time) became the first country in the world to introduce mandatory vaccination, in 1802. The Great Smallpox Pandemic of the 1870s was the last outbreak of the disease to reach pandemic level across Europe. Unbeknownst at the time, this would mark the last ever recorded case of naturally occurring smallpox in Iceland, in 1872. This made Iceland the first country in the world to eradicate the disease on a national level; the same factors that had allowed smallpox to be so devastating to Iceland's population in the past (i.e. distance from mainland Europe and a highly concentrated population) had become the reason why vaccination was so effective in the nineteenth century.