 This study will enroll healthy adults who have low pre-existing serum antibody titers to human parainfluenza virus type 3 HPIV3. Participants will be enrolled sequentially in two cohorts. Cohort 1 will receive two doses of 106.0 PFUmL of HPIV3-EbovZ GP, approximately 4-8 weeks apart. Cohort 2 will receive two doses of 107.0 PFUmL of HPIV3-EbovZ GP, approximately 4-8 weeks apart. 