Despite vaccination, Covid herd immunity unlikely in 2021: WHO Despite vaccination, Covid herd immunity unlikely in 2021: WHO Scientists at the World Health Organization warned Monday that mass vaccinations would not bring about herd immunity to the coronavirus in 2021. advertisement UPDATED: January 12, 2021 05:11 IST Scientists typically estimate that a vaccination rate of about 70% is needed for herd immunity, where entire populations are protected against a disease. But some fear that the extremely infectious nature of Covid-19 could require a significantly higher threshold. (Photo: Reuters) The World Health Organization's chief scientist warned that even as numerous countries start rolling out vaccination programs to stop Covid-19, herd immunity is highly unlikely this year.