The purpose of this study is to evaluate the safety, tolerability, and immune response to three different HIV-1 prime-boost vaccine regimens in healthy, HIV-1-uninfected adults. The regimens will differ by the type of HIV-1 envelope insert (Nat-B env, CON-S env, or Mosaic env) contained in both the DNA prime vaccine and the NYVAC boost vaccine.~The study will enroll 180 healthy, HIV-1-uninfected adults in two stages (Part A and Part B). After Part A of the study is fully enrolled, study researchers will evaluate study immunogenicity data to determine whether to enroll participants into Part B. The study design and vaccination schedule for both parts of the study will be the same.~Participants will be randomly assigned to one of three groups and receive either one of the experimental vaccine regimens or a placebo vaccine regimen. Participants will receive four total injections: on Day 0 and Day 28 (DNA vaccine or placebo) and on Day 84 and Day 168 (NYVAC vaccine or placebo). Group 1 participants will receive DNA Nat-B env and NYVAC Nat-B env vaccines, Group 2 participants will receive DNA CON-S env and NYVAC CON-S env vaccines, and Group 3 participants will receive DNA Mosaic env and NYVAC Mosaic env vaccines.~Total study duration will be either 3 years after enrollment (for participants in the United States) or 5 years after enrollment (for participants in Switzerland). For all participants, study visits will occur on Days 0, 14, 28, 42, 84, 98, 168, 175, 182, 273, 357, and 364. After the last study visit, participants will be contacted annually by phone or e-mail for a total of 3 (U.S. participants) or 5 (Switzerland participants) years to answer questions about their health.~At screening, participants will give a medical history; undergo a complete physical exam, blood collection, urine collection, and an electrocardiogram (ECG); and receive risk reduction counseling. At most follow-up visits, participants will undergo an abbreviated physical exam, blood collection, urine collection, and receive risk reduction counseling. Participants will have additional ECGs on Days 98 and 182. At all visits, female participants who were born female will be assessed for pregnancy prevention, and at select visits, will undergo a pregnancy test.
The purpose of this study is to test the safety and immune response to three different sets of HIV vaccines in healthy, HIV-uninfected adults.