who discovered the fact that people could be immunised against diseases?

Question: who discovered the fact that people could be immunised against diseases?
- Keywords:
  discover,
  disease,
  immunise
Asked by skyler and ben to Ben on 15 Mar 2018.
- Ben Mulhearn answered on 15 Mar 2018:
  
  I’m not sure who discovered that, but the most recent immunisation is against a virus called HPV, it protects against cervical cancer, which is great!

Question: who discovered the fact that people could be immunised against diseases?