An Investigational Immuno-therapy Study to Investigate the Safety and Effectiveness of Nivolumab, and Nivolumab Combination Therapy in Virus-associated Tumors

The purpose of this study to investigate the safety and effectiveness of nivolumab, and nivolumab combination therapy, to treat patients who have virus-associated tumors. Certain viruses have been known to play a role in tumor formation and growth. This study will investigate the effects of the study drugs, in patients who have the following types of tumors: * Anal canal cancer-No longer enrolling this tumor type * Cervical cancer * Epstein Barr Virus (EBV) positive gastric cancer-No longer enrolling this tumor type * Merkel Cell Cancer * Penile cancer-No longer enrolling this tumor type * Vaginal and vulvar cancer-No longer enrolling this tumor type * Nasopharyngeal Cancer - No longer enrolling this tumor type * Head and Neck Cancer - No longer enrolling this tumor type