It doesn’t mean 5% of vaccinated people get infected.
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?
It’s not just an academic question. How people understand these numbers affects how they think about the vaccine, whether they get it and how they behave after getting it, all of which have implications for the pandemic on a larger scale.
So how should people interpret these numbers?