Delta Variant on Track to Becoming Dominant Strain Worldwide Listen Download Embed Share Share this on Facebook (Opens in a new window) Share this on Twitter (Opens in a new window) Share this via Email In this March 27, 2021 file photo a laboratory worker simulates the workflow in a cleanroom of the BioNTech Corona vaccine production in Marburg, Germany, during a media day. ( AP ) Produced by Meg Dalton Hosted by Dr. Melissa Harris-Perry Produced by GBH, PRX and WNYC Studios