Five patients dialyzed at Boston Medical Center received phone calls saying they may have been exposed to Hepatitis B, NBC News reported.

"I'd probably only been home an hour and the phone rang and it was a gentleman from BMC, telling me that I had been exposed to Hepatitis B because their dialysis machine hadn't been cleaned properly," Joan Cooper told NBC.

(Study shows dialysis patients often get inappropriate antibiotic prescriptions)

The hospital told the Boston Globe that they "became aware that a small number of patients were potentially exposed to (the) Hepatitis B virus and five patients are potentially at risk from the exposure."

The hospital told Cooper she needed an injection of gamma globulin, a solution of antibodies that could combat the virus, and BMC sent a person to her home on Friday to administer the shot, Cooper told the Boston Globe.