For the third time in about six months, we’ve seen the World Health Organization (WHO) change the definition of herd immunity on their website (check here for definitions from June 9, 2020 and November 13, 2020).
On December 31, 2020, WHO defined it this way:
‘Herd immunity’, also known as ‘population immunity’, is the indirect protection from an infectious disease that happens when a population is immune either through vaccination or immunity developed through previous infection. WHO supports achieving ‘herd immunity’ through vaccination, not by allowing a disease to spread through any segment of the population, as this would result in unnecessary cases and deaths.
So what is WHO up to? Why so many revisions for a simple scientific truth?
Or are they correcting an error from the November 13 published definition?
Will fourth time be the charm?