Vaccine Efficacy. What it really means.
From the CDC.
A statement that was found from the ABC COVID site which was most interesting.
Why vaccine efficacy and effectiveness are not the same thing.As David Spiegelhalter, the chair of the Winton Centre for Risk and Evidence Communication at Cambridge University, and Anthony Masters, a statistical ambassador for the Royal Statistical Society,
outlined in The Guardian, a 90 per cent efficacy rate does not mean an individual has a 10 per cent chance of contracting COVID-19.
"Imagine 100 people are ill with COVID-19," the experts explained. "‘Ninety per cent efficacy' means if only they'd had the vaccine, on average only 10 would have got ill.
"Vaccine efficacy is the relative reduction in the risk: whatever your risk was before, it is reduced by 90 per cent if you get vaccinated. There is a lot of confusion about this number: it does not mean there is a 10 per cent chance of getting COVID-19 if vaccinated — that chance will be massively lower than 10 per cent."