When the syndrome that would ultimately be recognized as AIDS was first reported in 1981, the disease had not yet been named, the etiologic agent was unknown, and thus, specific treatments were not available. Since the early 1980s, major investments in observational science, discovery and innovation science, and implementation science have resulted and continue to result in substantial progress in the development of strategies for HIV prevention, treatment, and care.
The seminal advances in discovery and innovation science over the years have led to the discovery of HIV as the etiologic agent of AIDS, as well as a profound understanding of the HIV replication cycle, HIV pathogenesis, and the full extent of HIV disease. Building on these fundamental discoveries, innovation science has led to novel, safe, and effective modalities for HIV treatment and prevention. These early studies provided the foundation for the more than 30 antiretroviral drugs available today which are approved by the U.S. Food and Drug Administration and other international regulatory agencies, including several single-pill formulations containing multiple drugs that are highly effective in treating HIV infection, as well as regimens to prevent and treat HIV-associated coinfections and comorbidities. With the advent of antiretroviral therapy (ART), effective suppression of viral load to an undetectable level can be achieved in the vast majority of persons with HIV. Today, an individual with HIV in their early- to mid-20s who is adhering to an ART regimen can expect to live an additional 50 years achieving a nearly normal lifespan compared with a life expectancy of 1–2 years during the early pre-ART years of the epidemic when patients usually presented to the health care system with advanced disease.
The relatively recent demonstration that treatment is an effective HIV prevention strategy represents another important innovation science advance. The HPTN 052, Opposites Attract, and PARTNER 1 and 2 studies showed that when the viral load of a person with HIV is suppressed by ART to an undetectable level, there is no risk of transmission of HIV to an uninfected sexual partner. These innovative studies provided the evidence-base for the now accepted principle that “Undetectable = Untransmittable (U = U).” Another significant HIV prevention tool is pre-exposure prophylaxis (PrEP). Landmark clinical trials, including the iPrEX, TDF2, Partners PrEP, and Bangkok Tenofovir studies, have demonstrated that PrEP decreases by >96% the risk of HIV acquisition by an uninfected individual at significant risk of HIV. Both treatment as prevention for people with HIV and PrEP for those at-risk of acquiring HIV are vital strategies in our comprehensive HIV prevention toolbox.
Although there is an urgent need to continue to pursue innovation science toward an HIV vaccine, an ART-free remission, and a cure, there remains a major challenge in the optimal implementation of the advances that we already have in the areas of HIV prevention, diagnosis, treatment, and care. It is clear that the arena of implementation is itself a science that addresses key questions in how best to translate scientific and clinical advances into strategies that could be adopted at the community level, especially among those populations most at risk of HIV. However, this also requires taking into account the subtle and not so subtle variations in populations around the world. A “one size fits all” approach does not work in implementing the toolkit of HIV prevention and treatment strategies that have been developed and tested over the past 4 decades. These approaches must be adapted for each at-risk population, (eg, men who have sex with men, injection drug users, transgender persons, and commercial sex workers) and further modified to address racial and ethnic, gender, cultural, socioeconomic, and geographic parameters within each of these groups. Successful implementation of HIV prevention and treatment strategies also must take into consideration the numerous additional challenges that must be overcome, including structural, legal, and societal barriers such as stigma, discrimination, criminalization, lack of access to health care, food insecurity, and homelessness.
Certain of these challenges are being addressed on a regional and international scale as demonstrated by the community-based implementation science projects conducted in Africa. These studies, uniquely designed to meet the needs of the local communities involved, were sponsored by the Centers for Disease Control and Prevention, the National Institutes of Health, and United States Agency for International Development with critical support from the President's Emergency Plan for AIDS Relief (PEPFAR).
In the United States, a new initiative, “Ending the HIV Epidemic: A Plan for America,” has recently been launched that targets a 75% reduction in new HIV infections in 5 years and at least a 90% reduction of new HIV infections by 2030. This multiagency initiative of the U.S. Department of Health and Human Services, similar to the PEPFAR program, will focus on community-based initiatives in the states, counties, and territories of the United States that accounted for more than 50% of the new HIV infections in 2016 and 2017. Implementation science will be essential to the successful achievement of the goals of this new initiative by translating evidence-based interventions, resulting from discovery and innovation science, into real-world practice.
This special supplement to the Journal of AIDS provides a forum to highlight the latest methodologies and analytical approaches, as well as the research challenges and opportunities to conducting implementation science in the context of both the global and domestic responses to HIV. In this regard, the research community is actively engaged in how best to integrate and implement these biomedical tools within the social and structural contexts and across all steps of the prevention and care continuum. As we move forward, knowledge gained through implementation science will be critical in defining and refining an evidence-based plan, to bring HIV prevention and treatment interventions to scale, and thus, achieve the goal of ending the HIV epidemic domestically and globally.