Precision medicine and precision public health focus on identifying and providing the right intervention to the right population at the right time. Expanding on the concept, precision prevention science could allow the field to examine prevention programs to identify ways to make them more efficient and effective at scale, including addressing issues related to engagement and retention of participants. Research to date on engagement and retention has often focused on demographics and risk factors. The current paper proposes using McCurdy and Daro (Family Relations, 50, 113-121, 2001) model that posits a complex mixture of individual, provider, program, and community-level factors synergistically affect enrollment, engagement, and retention. The paper concludes recommending the use of research-practice partnerships and innovative, rapid cycle methods to design and improve prevention programs related to participant engagement and retention at scale.

Objectives To describe the characteristics and evidence of comprehensive adolescent health (CAH) programs encompassing sexual and reproductive and other health services, educational and social support. Methods Systematic review of peer-reviewed and grey literature on CAH programs (1998-2013). Only programs with experimental, quasi-experimental or pre-post evaluations were included. Two independent reviewers screened 36,119 records and extracted articles using predefined criteria. Data was synthesised into descriptive characteristics; quality was assessed by evidence level (rigorous, strong, modest). Results Data was extracted on 46 programs (181 studies) of which 19 programs were defined as comprehensive; 9 were excluded due to insufficient evaluations. Ten CAH programs met all inclusion criteria. Most were US based; others were implemented in Egypt, Ethiopia and Mexico. Few programs (N=3) displayed rigorous evidence, 5 had strong and 2 had modest evidence. All programs with rigorous/strong evidence directly or indirectly influenced adolescent sexual and reproductive health. Common elements of these programs included: long-term commitment to adolescents, interpersonal connections, community mobilization, and skill-building elements. Conclusion The long term impact of many CAH programs cannot be proven due to insufficient evaluations. Evaluation approaches that take into account the complex operating conditions of many programs are needed to better understand mechanisms behind program effects.