What’s the science behind CDC’s decision to say fully vaccinated people don’t need masks?

A fresh batch of data from a big study of health care workers across the country helped prompt the US Centers for Disease Control and Prevention to say fully vaccinated people can go without masks in most circumstances, the agency said Friday.A fresh batch of data from a big study of health care workers across the country helped prompt the US Centers for Disease Control and Prevention to say fully vaccinated people can go without masks in most circumstances, the agency said Friday.