“We need to do our utmost so that the benefits of the new treatments can reach those poorest people in Africa and in the rest of the world” said Jacques Chirac, former French President, at the tenth International Conference on AIDS and STIs in Africa (ICASA), held in December, 1997, in Abidjan, Cote d'Ivoire. 20 years on, Abidjan is again hosting ICASA, with one aim: “Africa: ending AIDS—delivering differently”.In two decades, new funding mechanisms have been developed and antiretroviral therapy (ART) has been scaled up exponentially. ART has been proven efficient in reducing mortality and morbidity, HIV transmission,1and HIV acquisition.2Social science contributed to show that access to ART was feasible, efficient, and acceptable in Africa.3Modelling research suggested that a universal test-and-treat strategy could potentially stop HIV transmission and end AIDS4—the goal of UNAIDS's 90-90-90 target for 2020.However, we are still facing major gaps. Biomedical innovations will be crucial, but not sufficient alone. Innovations in terms of intervention implementation, delivery models, and public health policies are urgently required. Such challenges are not just operational, logistic, or politic. Beyond effectiveness, we need empirical and theoretical knowledge about implementation.5We also need social science research, both fundamental and operational, to analyse social, cultural, political, and structural processes that still limit access to prevention and care.Long-term perspective is needed to understand present limitations of HIV services, despite the huge funding devoted to HIV response by global institutions. How global health policies could jeopardise local response in some areas? Why perceived stigma is still a major barrier to care and services as it was 20 years ago? This issue is particularly true for western and central Africa, which received historically less attention than eastern and southern Africa6and where gaps are more pronounced: among people living with HIV in 2016, only 42% knew their status, 35% were on treatment, and 25% were virally suppressed in western and central Africa, versus 76%, 60%, and 50%, respectively, in eastern and southern Africa.7These issues were raised at the Social Science and HIV/AIDS in Sub-Saharan Africa conference, hosted in Abidjan in December, 2016. To fully play their part, social and implementation sciences must embrace the key questions raised by contemporary epidemics and that cannot be solved by biomedical science alone, including stigma, therapeutic failure, people-centred approaches, ageing of people living with HIV, integration of HIV services, governance and funding, and implementation of universal health coverage. Dedicated funding for coordination, research networks, and both operational and fundamental social science research is essential.We, scientists in social and implementation science, on behalf of the Abidjan 2016 conference scientific committee, would like to reaffirm the importance of multifaceted and plural social sciences and to keep such research on the international scientific agenda, in particular for western and central Africa. We hope that the 2017 ICASA conference held in Abidjan this week will provide a forum to discuss such matters.We declare no competing interests. We are members of the Social Science and