VRE bacteria actually only rarely cause illness in healthy humans. The problems occur when it has contact with an open wound or skin sore and VRE can then cause infection in the would or sore. On more rare occassions it can cause a serious infection of the blood or body tissues.
Vancomycin is a powerful antibiotic used in the treatment of such infections. Vancomycin is necessary to treat enterococci related infections because this bacteria is resistant to many other antibiotics. Of course, as you might gather from its name VRE can also become resistant to Vancomycin and the drug will not be successful and the infection will be very difficult to treat.