BACKGROUND: There are limited data that evaluate how pharmacists who are integrated within primary care clinics influence proportion of days covered (PDC) and Part D star ratings for the 3 adherence measures: diabetes, hypertension (renin-angiotensin-system antagonists), and cholesterol (statin) medications. OBJECTIVE: To assess the difference in percentage of beneficiaries with a prescription with a PDC of 80% or higher in the adherence prioritization group versus control group. METHODS: A retrospective cohort study was conducted that collected data from 2019 monthly and end-of-year files provided by Humana Medicare Advantage (MA) Part D for patients attributed to a Banner Medical Group (BMG) primary care provider who filled at least 1 prescription for a medication included in any of the medication adherence classes. The Banner Pharmacy Services population health team prioritized beneficiaries and provided worklists to pharmacists embedded in the BMG primary care clinics in Colorado. The pharmacists performed telephonic outreach, which included patient education, along with leveraging of pharmacist-provider collaborative practice agreements to address barriers, facilitate refills, and convert prescriptions to 90-day supply and mail order. Outreach status was tracked. Colorado patients reached at least once during the study time frame served as the adherence prioritization group, while Arizona patients were propensity score matched and served as the control group. We evaluated the effects of contact with the pharmacist on adherence between the adherence prioritization and control groups with PDC as a binary variable (≥ 80% vs. not) and a continuous variable (0%-100%). Analysis with PDC as a binary variable was also completed for the entire Humana MA Part D cohort. RESULTS: A total of 881 unique patients with prescriptions that fell into one of the medication adherence classes were included in the analysis-294 in the adherence prioritization group and 587 in the control group. Baseline demographics were well balanced between groups. Across the 3 medication classes, the adherence prioritization group had a higher percentage of patients with PDC of 80% or higher (71.0%) versus the matched control group (62.3%), a difference of 8.6% (95% CI = 3.47-13.82, P < 0.001). End-of-year data for the adherence prioritization population shows the percentage of patients who passed the medication adherence measure for diabetes, hypertension, and cholesterol was 88%, 89%, and 89%, respectively, while in the control population passing rates were 85%, 88%, and 87%, respectively. CONCLUSIONS: Pharmacist-driven interventions can have a meaningful effect on PDC for medication adherence and can ultimately affect star rating measures. Since 2019 data are used for 2021 star rating measures, even small numerical differences as seen in this study may account for the difference between a 4- or 5-star rating. Moving the needle in the right direction can be significant, since the cut point is yet to be determined. DISCLOSURES: This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Rinehart, Rice, and Collins are employed by Banner Health but received no specific financial incentives or otherwise related to this research and manuscript. Glover is employed by Pfizer, which had no role in this study. The authors have no other relevant declarations of interest to disclose. This study was presented as a platform presentation at the Southwestern States Residency Conference, June 2020, Phoenix, AZ.