Keep in mind, while the residents of elderly care facilities are generally staying there, many others come and go regularly. The staff working there go home every night, go shopping, visit friends and family, etc. They’re in the community as much as any of us. Friends and family of the residents themselves also visit and are otherwise in the community. And anyone delivering things to the nursing home, maintenance personnel, administrators, inspectors, etc. All of them come in from the outside.
There’s a reason we’ve had such trouble keeping this bug out of nursing homes despite the high cost. That, and Governor Cuomo forcing nursing homes to accept known infected patients. But that’s another story.
CDC currently reports 10 covid vaccine deaths through the end of December.