Answer:
Vaccination.
Step-by-step explanation:
Inoculation causes Mild disease in a human body. Antibodies develop in response to the disease and the disease is cured. The long term benefit is that, the individual develops immunity to small pox as well- a disease much deadlier than cowpox and can be fatal even.
Thus this individual will never have smallpox in his lifetime. This is because cowpox and smallpox virus are very closely related in their structure.