900-person delta cluster in Mass. of which 74% are vaccinated https://arstechnica.com/science/2021/07/this-900-person-delta-cluster-in-mass-has-cdc-freaked-out-74-are-vaccinated/ This incident is reported on CDC website: https://www.cdc.gov/mmwr/volumes/70/wr/mm7031e2.htm?s_cid=mm7031e2_w