PROJECT SUMMARY Healthcare provider (HCP) recommendations are one of the most important factors influencing parents’ acceptance of adolescent vaccines. A large body of literature across qualitative, observational and intervention studies has demonstrated that parents who receive a vaccine recommendation from a healthcare provider are much more likely to vaccinate their child. However, provider recommendations are not universal and high- quality recommendations are even more uncommon. Provider recommendations for adolescent vaccines can vary in strength, consistency, and timeliness, but the factors that influence the frequency and quality of these recommendations have not been well explored. The vaccine decision making process is influenced by factors at multiple levels including the individual, interpersonal, and community levels. Provider vaccine recommendations can be conceptualized in the same way–HCPs are influenced not only by their own attitudes and knowledge about the vaccine, but also their perceptions and knowledge of the patient and community in which they practice. Additionally, these factors do not work in isolation and can interact across levels to influence recommendations. In the proposed project, we will conduct a sequential mixed-methods study to explore how provider recommendations vary by individual, interpersonal and community level factors. First, we will conduct a multi- level analysis of nationally-representative zip code level data from NIS-Teen to examine how provider recommendations vary by interpersonal factors (i.e. patient characteristics - race/ethnicity, education level, insurance coverage) and community-level factors (i.e. urbanicity, poverty level) as well as how these factors interact (Specific Aim 1). To better understand our findings from Aim 1, we will conduct in-depth interviews with adolescent HCPs to explore how individual-level factors (i.e. provider attitudes) inform interpersonal and community level variation (Specific Aim 2). These interviews will be conducted in New Haven County among HCPs who both represent and provide service to a socio-demographically diverse population. Through this sequential mixed-methods approach, we will identify both how provider recommendations vary as well as explore the underlying beliefs and biases that guide provider recommendation practices. So far, research has primarily focused on the impact of provider recommendations for the HPV vaccine; examining the entire adolescent vaccine platform in this proposal will allow us to expand this limited body of literature. Our results will provide a foundation for the development and targeting of interventions to improve the quality of provider recommendations for greater coverage for all adolescent vaccines.