We have statistics about Case Fatality Rate (Death rate) of a disease for 30 years totalling to about 30,000 cases. Then, a new treatment was planned and started. Now we have 10 years statistics of Case Fatality Rate totalling to about 10,000 cases.
I want to compare and draw statistical conclusions about the efficacy of the treatment.
What statistical tests I will have to use. Please advise me.

I will add one more point. If the Case Fatality Rate is Zero after starting treatment, how do we calculate