This proposal outlines the scientific agenda of the Leadership and Operations Center of the HIV Vaccine Trials Network (HVTN), the collaboration of physician scientists at 64 clinical trial sites in 15 countries on 4 continents dedicated to developing a globally effective HIV vaccine. During the current funding period, the HVTN has transformed HIV prevention science by taking two HIV vaccine concepts and the broadly neutralizing monoclonal antibody (mAb) VRC01 from phase 1 to efficacy evaluation. We have added over 35 clinical trial sites in sub- Saharan Africa and now have over 12,500 participants enrolled in randomized controlled efficacy trials. We propose to continue our scientific leadership in HIV vaccines. The scientific pipeline for vaccines with the potential to induce broadly neutralizing antibodies (bnAbs) to HIV has markedly expanded. This proposal describes a novel fast-track phase 1 program to assess, in an iterative fashion, candidate trimers, germline or lineage-based vaccines designed to elicit bnAbs in adults. A phase 1 program to investigate these vaccines in HIV-1–exposed infants is also proposed. The HVTN currently has five HIV efficacy trials in place. Two vaccine trials (HVTN 702 & 705) are in progress; a third (HVTN 706) will start in August 2019; and we are collaborating with the HIV Prevention Trials Network (HPTN) on two antibody-mediated prevention (AMP) trials evaluating the infusion of passively administered mAbs. These efficacy trials will define the potential of neutralizing and/or non- neutralizing antibodies to prevent HIV acquisition. The samples and statistical design of the efficacy trials are developed around correlates of protection; we will continue to develop the robust integrated laboratory, statistical and computational platform needed to define these correlates. We will also continue to expand our behavioral sciences program to enhance our already successful recruitment and retention programs, and to continue to expand the enrollment of persons of color and transgender persons into HVTN trials. Vaccine clinical trials involve a complex interplay between clinical trial sites, HVTN laboratories, computational scientists, and our operational, training, mentoring, and fiscal management teams; these interactions are described in the application. The clinical, laboratory and statistical infrastructure we have built for HIV vaccines will also be used to assist in tuberculosis (TB) vaccine development. Importantly, we will build on our success in the unique community-based programs and integration of community representatives and community advisory boards into HVTN research process and conduct. We will also continue to develop the next generation of vaccine scientists and expand our scientific collaborations to engage the scientific community to utilize the extensive specimen and data repositories we have established. The overall goal of the HVTN in this proposal is to develop a vaccine regimen or combination m...