Communicating effectiveness of boosters

November 22, 2021

Topic

Statistics  /  , , , ,

Statisticians David Spiegelhalter and Anthony Masters for The Guardian on reframing risk estimates:

An earlier UKHSA study estimated two Pfizer/BioNTech doses gave around 99.7% (97.6% to near-100%) protection against Delta-infected hospitalisation, but after 20 weeks that effectiveness waned to 92.7% (90.3% to 94.6%). This estimated decline for people over 16 may not sound much, but if we look at it in terms of “lack of protection”, their estimated vulnerability relative to being unvaccinated went from 0.3% to 7.3%. That is a major, although uncertain, increase in risk.

Such “negative framing” can change impressions: “90% fat-free” sounds rather different than “10% fat”.