This multicenter clinical trial will examine whether a vaccine (“Triplex”) for a common viral infection (cytomegalovirus [CMV]) will be safe, effective and elicit CMV-specific immunity, and decrease the need for toxic CMV antiviral therapy in liver transplant recipients who are at high risk for CMV infection. If shown to be effective, this vaccine could be used as a way to better prevent CMV infection in transplant recipients and other populations with weakened immune systems who are at risk for CMV infection.