WHO changed the definition of herd immunity at least twice since the start of the pandemic.
November 2020 https://web.archive.org/web/20201124094747/https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-serology
Now https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-serology
WHO changed the definition of herd immunity at least twice since the start of the pandemic.
June 2020
https://web.archive.org/web/20201101161006/https:/www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-serology
November 2020
https://web.archive.org/web/20201124094747/https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-serology
Now
https://www.who.int/news-room/q-a-detail/coronavirus-disease-covid-19-serology
(post is archived)