A 900-person Covid delta cluster in Massachusetts includes 74% vaccinated people

An alarming Washington Post article says the Covid-19 delta variant is "so contagious that it acts almost like a different novel virus, leaping from target to target more swiftly than Ebola or thecommon cold."

Ars Technica says an internal CDC report paints a grim picture:

An analysis of a COVID-19 cluster of around 900 people in Massachusetts74 percent of whom are vaccinatedis among the alarming data that spurred the Centers for Disease Control and Prevention toreverse course on masks this week.