The phrase "efficacy rate" refers to how effective or successful something is in producing the desired result. It is a measurement of how well a particular treatment, medicine, or intervention works in achieving its intended purpose. Full definition
In the new study, the method accurately predicted vaccine efficacy rates for more than 40 years of flu records. (sciencedaily.com)
They are popular choices because of the high efficacy rate: they kill the parasites. (petbusiness.com)
The vaccines had a 93 % efficacy rate in the clinical trials we performed, and are an alternative to radiation therapy with or without surgery. (vetmed.umn.edu)