COVID-19 vaccines: What does 95% efficacy actually mean?

COVID-19 vaccines: What does 95% efficacy actually mean?

COVID-19 vaccines: What does 95% efficacy actually mean?

You have likely heard that Pfizer’s COVID-19 vaccine efficacy is 95%, Moderna’s is 94% and Johnson & Johnson’s is 66%. But what do these numbers actually mean?
COVID-19 vaccines: What does 95% efficacy actually mean?