The skeptic in my head has been saying for years, “How can I measure security efficacy in the real world?” Here’s how.
First, it is important to know that efficacy is measured by calculating the “proportionate reduction in risk.” In the case of COVID-19 vaccines, for example, that occurs when assessing the outcome of applying treatment to one population as compared to an untreated population. That meant monitoring the effect of giving either the real vaccine or a placebo to 30,000 to 40,000 people for each vaccine (population requirements were determined statistically) and assessing the outcomes. With both Pfizer and Moderna, the vaccines resulted in about 95% fewer COVID cases, so that is their efficacy. You can find the efficacy data of all sorts of treatments against all sorts of illnesses and diseases.