Beth Israel Deaconess Medical Center in Boston is closing one of its floors less than a month after laying off more than 20 employees, changes that are causing some concerns among union officials.

Beth Israel Deaconess physicians join their peers at Boston Medical Center, the UMass Chan Medical School, and Cambridge Health Alliance, who have also voted to unionize.

Residents and fellows at Beth Israel Deaconess Medical Center voted to unionize with 83 percent in favor on Wednesday, joining the Service Employees International Union’s Committee of Interns ...