Context Vaccination status has been shown to be linked to patient-centered outcomes in those with COVID-19. However, minimal data have explored the relationship between vaccination status and representation rates after receiving monoclonal antibodies (MABs) the Delta strain of severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) in a community setting. Objectives The authors sought to determine if there was a difference in patient-centered outcomes between those who were vaccinated and unvaccinated after the administration of casirivimab/imdevimab for mild-to-moderate COVID-19 during the time when the Delta strain was most prevalent. Methods A convenience sample of consecutive adults given casirivimab/imdevimab at either an outpatient infusion center or within the emergency department (ED) were included in analysis. Patient demographics, authorized-use qualifiers from the emergency use authorization (EUA), baseline vital signs at the time of infusion, representation rates to a healthcare provider within the hospital’s network, and any admissions to the hospital following infusion were all collected from the patient’s electronic medical record. Vaccination status was confirmed in both the patient’s electronic medical record and the Arizona State Immunization Information System (ASIIS). Analysis was conducted utilizing descriptive statistics, the Mann–Whitney U test for continuous data, and the chi-squared analysis for nominal data. Results In total, 743 patients were included in the study, with 585 being unvaccinated and 158 being vaccinated at the time of administration. Those in the vaccinated group were more likely to be older (60.0 vs. 55.0 years; p<0.001) and to have a history of diabetes (18.4% vs. 11.3%; p=0.02), hypertension (39.9% vs. 28.5%; p=0.006), immunosuppression (7.0% vs. 1.4%; p<0.001), and chronic kidney disease (7.0% vs. 3.4%; p=0.05). In the entire sample, 105 (14.1%) patients had an unexpected return visit to either the ED or urgent care at 28 days, with 17 (2.3%) requiring hospitalization. Patients who were vaccinated were more likely to represent for care after casirivimab/imdevimab infusion (20.3% vs. 12.5%; p=0.01), but no difference was noted in hospitalization rates between the two groups (18.8% vs. 15.1%; p=0.15). Conclusions MAB therapy with casirivimab/imdevimab for the outpatient treatment of mild-to-moderate COVID-19 was associated with a low rate of hospitalization. However, those who were vaccinated were more likely to present for unexpected return care at either the ED or urgent care within 28 days of the initial infusion.

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