Vaccine Efficacy Estimates

What does a ‘95% effective’ vaccine mean?

News reports shared trial findings of different vaccinations against COVID-19. For example, a BBC headline on 16th November was:

This article looks at what statements about ‘95% protection’ and similar claims mean. This is another way of phrasing vaccine efficacy. It also shows how to calculate approximate uncertainty around those central estimates.

What is vaccine efficacy?



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Anthony B. Masters

This blog looks at the use of statistics in Britain and beyond. It is written by RSS Statistical Ambassador and Chartered Statistician @anthonybmasters.