Strategies to combat COVID-19 include vaccines and Monoclonal Antibody Therapy. While vaccines aim to prevent development of symptoms, Monoclonal Antibody Therapy aims to prevent the progression of mild to severe disease. An increasing number of COVID-19 infections in vaccinated patients raised the question of whether vaccinated and unvaccinated COVID-19 positive patients respond differently to Monoclonal Antibody Therapy. The answer can help prioritize patients if resources are scarce. We performed a retrospective study to evaluate and compare the outcomes and risks for disease progression between vaccinated and unvaccinated COVID-19 patients treated with Monoclonal Antibody Therapy by measuring the number of Emergency Department visits and hospitalizations within 14 days as well as the progression to severe disease, defined through the Intensive Care Unit admissions within 14 days, and death within 28 days from the Monoclonal Antibody infusion. From 3898 included patients, 2009 (51.5%) were unvaccinated at the time of Monoclonal Antibody infusion. Unvaccinated patients had more Emergency Department visits (217 vs. 79, p < 0.0001), hospitalizations (116 vs. 38, p < 0.0001), and progression to severe disease (25 vs. 19, p = 0.016) following treatment with Monoclonal Antibody Therapy. After adjustment for demographics and comorbidities, unvaccinated patients were 2.45 times more likely to seek help in the Emergency Department and 2.70 times more likely to be hospitalized. Our data suggest the added benefit between the COVID-19 vaccine and Monoclonal Antibody Therapy.

Background Strategies to combat COVID include vaccines and Monoclonal Antibody Therapy (MAB). While vaccines aim to prevent symptom development, MAB aims to prevent progression of mild symptoms to severe. Increasing numbers of COVID infections in vaccinated patients raised the question of whether vaccinated and unvaccinated patients respond differently to MAB. Methods We performed a retrospective review of the medical charts to evaluate responses of MAB in vaccinated and unvaccinated COVID patients by measuring the number of emergency department (ED) visits, hospitalizations, and ICU admissions within 14 days and the 30-day mortality following MAB. We evaluated outcomes according to vaccination status using absolute risk reduction and used Chi-squared tests to assess statistical significance using an alpha of p&lt; 0.05. We used multivariable generalized linear models with a log link and binomial distribution to estimate adjusted relative risk and 95% confidence intervals. Figure 1:Subject Flow Diagram Results Based on the inclusion criteria, we found 4,128 patients from which 230 had missing vaccination information or dose. From 3898 included patients, 296 (7.59%) visited the ED, 154 (3.95%) were hospitalized, and 25 (0.64%) were in ICU within 14 days of infusion. 12 patients (0.31%) died within 30 days. 2009 (51.5%) were unvaccinated at the time of infusion. Demographics were similar in both groups except that most of the patients in both groups were Non-Hispanic Caucasians, raising the question of racial and ethnic disparities. All comorbidities except pregnancy were predominant in the vaccinated group. Unvaccinated patients were more likely to receive MAB after 7 days of symptoms and in the ER, suggesting that they may have had more severe disease at the time of infusion, despite having less comorbidities. Unvaccinated patients had more ED visits (11.2% vs 4.3%, p&lt; 0.0001), hospitalizations (6.2% vs 2.1%, p&lt; 0.0001), and deaths (1.1% vs 0.3%, p=0.005) following infusion. Adjusted for demographics and comorbidities, unvaccinated patients were 2.41 times more likely to seek help in the ED and 2.73 times to be hospitalized. Figure 2:Patient Demographics and ComorbiditiesFigure 3:Comparison of Outcomes by Vaccination StatusFigure 4:Relative Risk by Vaccination Status Model 1 – Unadjusted Model 2 – Adjusted for financial class, infusion location, patient sex, patient age, patient race, and time to infusion Model 3 – Model 2 Variables + Comorbidity Count Model 4 – Model 2 + Specific Comorbidities (diabetes, cancer, immunosuppression, BMI, chronic kidney disease, cardiovascular disease, lung disease, neurological disorders, and smoking) Conclusion Our data confirms that immunization plays a key role in reducing COVID-related morbidity and mortality. It also supports MAB efficiency from clinical trials. Figure 5:Future Actions Disclosures All Authors: No reported disclosures.