Smallpox 40 years on

Today marks the 40th anniversary of the last recorded fatal case of smallpox, the first disease to be eradicated through vaccination.

Smallpox is caused by the Variola virus, and was the first virus to be targeted by vaccination. It is a highly contagious Poxvirus, transmitted by airborne virus particles, and has around 30% mortality rate.

Records of variolation, the method of inoculating people with samples of smallpox from infected individuals, go back centuries. Many people have heard the story of Edward Jenner (1749-1823), the physician who famously used the closely-related cowpox virus as the first vaccine (and he is also the namesake of the institute where I now work!). Jenner observed that milkmaids, who spent a lot of their time around cows, rarely caught the much more deadlier smallpox. Through the first ever clinical vaccine trial, and one that would never be approved by ethics committees today,  Jenner used cowpox virus material (closely related to Variola virus) to inoculate a young boy, and then infected him with smallpox. The boy remained healthy, and the smallpox vaccine was considered a success.

As of 1950, smallpox caused 50 million cases  per year worldwide. From 1967, the WHO (World Health Organisation) undertook a mass vaccination schedule, using a live Vaccinia virus not too dissimilar from the one Jenner used. Smallpox was declared eradicated in 1980, and all samples are now stored as BSL-IV containment.



Further reading:

Morabia, A. Edward Jenner’s 1798 report of challenge experiments demonstrating the protective effects of cowpox against smallpox. Journal of the Royal Society of Medicine. 2018.


Image: wikimedia commons


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