Overall, 68. 2% of eligible persons in the census populations in the six study sites accepted our invitation to enroll and participate in the cross-sectional study. gender, marital status, level of education, Endothelin-2, human and sex under substance influence as significant risk factors for HIV (p <0. 001). Educating and winning the trust of local community leadership ensured high level of participation (53. 377. 9%) and willingness to participate in future studies (95%). The high HIV prevalence and high risk of HIV infection at highway settlement and mammy markets make them well suited for targeting future vaccine trials in Nigeria. == Introduction == A recent UNAIDS report for 2014 estimated that 36. 9 million people worldwide were living with HIV including 2 . 0 million people newly infected in 2014 [1]. Hardest hit by theHIV/AIDSpandemic is sub-Saharan Africa where the disease continues to devastate communities, thereby rolling back decades of economic development [2, 3]. Nigeria, the most populous country in this region has an estimated 3. 2 million people living with HIV disease, (national HIV prevalence of 3. 4%), and carries the second highest burden of HIV/AIDS in the world [1]. Despite the downward trend in overall HIV prevalence, moderate to severe epidemics persist in the 36 States and Federal Capital Territory of Nigeria, with over 10% prevalence in the general population in some States [2, 4]. Durable elimination of the HIV pandemic will require new combination prevention strategies including development of a globally effective vaccine, coupled with other proven biomedical and behavioral interventions [5]. Previous and on-going vaccine studies by the US Military HIV Research Program (MHRP) had been in Thailand where the epidemic is Endothelin-2, human mainly due to HIV-1 subtype CRF01_AE and in East Africa dominated by subtypes A, C, D and intersubtype recombinants. These strategies will need to be expanded to protect against other subtypes and Endothelin-2, human account for other regions such as West Africa with its unique HIV-1 circulating subtypes [610]. Some research studies previously conducted in Nigeria, such as the failed Pfizer trials of 1996, lacked the required IRB regulatory approvals and documented evidence of informed consent [1113]. Any future trials and vaccine studies, therefore , must ensure appropriate community engagement, site preparedness and adherence to the principles of Good Participatory Practice (GPP) to restore the trust of the community [14]. The aim of this study was to identify populations with high HIV prevalence and at high risk for HIV infection for vaccine cohort development in Nigeria; assess the level of interest of populations to participate; and, engage support of local stakeholders. Specific objectives of the study included estimation of the distribution of HIV subtypes and prevalence of Hepatitis B and C in the study population. Follow up incidence studies in key populations at risk for HIV infection will further inform vaccine development in Nigeria. == Methods == This cross-sectional observational study commenced in 2009 and was initiated at six sites (Makurdi, Abuja, Enugu, Kaduna, Tafa and Ojo-Lagos) distributed across four States and the Federal Capital Territory of Nigeria. The initial population evaluated focused on market sites in proximity of selected military hospitals and PEPFAR Centers including mammy markets run by civilians, and neighboring bars, hotels, and restaurants, where many people congregate with opportunities for social interactions. Two additional sites at highway settlements were later added to provide access to populations at higher risk of HIV infection. Gaining approval from civil authorities at the Federal, State and Local levels, and from community and military leaders prior to study implementation at each site helped population acceptance of the study. While the institutional partners provided general awareness, legitimacy, and letters of support, community leaders and community associations were instrumental in the mobilization of study participants. The field study commenced with advocacy visits, key informant interviews, and focus group discussions. The owners and Endothelin-2, human managers of businesses in all the fixed structures to DNAJC15 include shops, bars, and guesthouses in the selected study area were asked to fill out a questionnaire about employees working at their premises. The Endothelin-2, human socio-demographic information of approximately 15, 400 individuals identified from.