You should do some research on vaccines.
The
smallpox vaccine is used to prevent smallpox infection caused by the variola virus.
[10] It is the first
vaccine to have been developed against a contagious disease. In 1796, British physician
Edward Jenner demonstrated that an infection with the relatively mild
cowpox virus conferred immunity against the deadly
smallpox virus. Cowpox served as a natural vaccine until the modern smallpox vaccine emerged in the 20th century. From 1958 to 1977, the
World Health Organization (WHO) conducted a global vaccination campaign that
eradicated smallpox,
[10] making it the only human disease to be eradicated. (wikipedia.smallpox.vaccine.)
One of the deadliest diseases known to humans, smallpox remains the only human disease to have been eradicated. Many believe this achievement to be the most significant milestone in global public health. Key components of the worldwide smallpox eradication effort included universal childhood immunization programmes in some countries, mass vaccination in others, and targeted surveillance-containment strategies during the end-game. Over thousands of years, smallpox killed hundreds of millions of people. The rich, the poor, the young, the old. It was a disease that didn’t discriminate,
killing at least 1 in 3 people infected, often more in the most severe forms of disease. The symptoms of smallpox were gruesome: high fever, vomiting and mouth sores, followed by fluid-filled lesions on the whole body. Death would come suddenly, often within 2 weeks, and survivors could be left with permanent harms such as blindness and infertility. in the most severe forms of disease. Mozart was infected, as was Abraham Lincoln. (who.history of smallpox vaccination)