Answer:
The correct answer would be a vaccine was developed.
A vaccine is a substance (usually a heat-killed or attenuated pathogen or antigen) which is injected into the body of the person in order to produce antibody and thus it develops immunity against that specific pathogen or disease.
A vaccine for smallpox was developed in 1796 by Edward Jenner which results in global eradication of smallpox.
Step-by-step explanation: