In a recent study published in the Annals of Internal Medicine, researchers assess the efficacy of monoclonal antibodies (mAbs) in treating coronavirus disease 2019 (COVID-19) caused by different viral variants.

Study: Evolving Real-World Effectiveness of Monoclonal Antibodies for Treatment of COVID-19: A Cohort Study. Image Credit: Nilsbwoy /

Study: Evolving Real-World Effectiveness of Monoclonal Antibodies for Treatment of COVID-19: A Cohort Study. Image Credit: Nilsbwoy /

Treating COVID-19 with mAbs

The use of mAb treatment has been shown to reduce severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral load and subsequently lead to lower rates of COVID-19-related hospitalization and death among high risk patients as compared to those who did not receive the treatment. The benefit of mAb treatment appears to be greatest in patients over 65 years old and those with a weakened immune system.

Observational clinical data on the use of mAb products among COVID-19 patients, particularly following the emergence of the Omicron variant, are scarce. Thus, there remains an urgent need to examine the efficacy of individual mAb products against new SARS-CoV-2 variants to identify patient populations that will benefit most from mAb treatment.

About the study

In the present study, researchers determine whether early outpatient mAb treatment is associated with a reduced risk of hospitalization or death due to COVID-19 at 28 days.

To this end, health data was analyzed from various clinical systems, including the electronic health record (EHR) and a clinical data warehouse. Sociodemographic data and medical history for both outpatient and inpatient cases were obtained for every patient. The study identified deaths at 28 days with hospital discharge dispositions for "ceased to breathe" obtained from the inpatient medical record system.

Patients who tested positive for COVID-19 in the University of Pittsburgh Medical Center (UPMC) health system between December 8, 2020, and August 31, 2022, were included in the current study. Additionally, patients aged 12 years or older who had at least one emergency use authorization (EUA)-eligible risk factor for severe disease, were not in the emergency department (ED) or hospital as of the index date, was not pregnant, had at least one record in the EHR from the previous year, and had almost-complete covariate information for analysis, were also included.

Patients were categorized and evaluated into treated or non-treated groups. Patients with COVID-19 were treated with various mAbs such as bamlanivimab, bamlanivimab-etesevimab, casirivimab-imdevimab, sotrovimab, or bebtelovimab at an outpatient infusion clinic. Primary study outcomes included the risk of hospitalization or death within 28 days, whereas secondary outcomes included hospitalization, ED visit without hospitalization, a combined outcome of ED visits or hospitalization within 28 days, or death.


The current study included 2,571 treated and 5,135 matched nontreated patients. After the one-, two-, and three-day treatment periods, 10.3%, 6.1%, and 3.2% of non-treated patients were treated with mAb therapy. The average age of treated individuals was 58.5 years, while the average age of nontreated patients was 49.3 years before 1:2 propensity score matching.

Treated patients had a greater overall risk profile than nontreated control patients before matching, with a higher prevalence of diabetes, obstructive sleep apnea, cancer, and hypertension. Furthermore, a higher proportion of treated individuals were immunocompromised than nontreated control patients.

Treated patients had a reduced risk of hospital admission or death at 28 days as compared to nontreated control patients with a risk ratio (RR) of 0.61. Treated patients were also less likely to be hospitalized or die, particularly after seven days from the index date. The lower RR related to mAb treatment was noted for the risk of hospitalization at 28 days and the risk for death at 28 days. The use of mAbs did not increase the risk of hospitalization or ED visits.

Patients who were treated with mAb therapy during periods of SARS-CoV-2 Alpha, Delta, and Omicron variant dominance were associated with RRs of 0.55, 0.53, and 0.71, respectively. Furthermore, RR estimates for individual mAb product treatment indicated a lower risk of hospitalization or death. The RR associated with hospitalization or death among immunocompromised patients was 0.45, which was slightly lower than the RR of 0.58 for non-immunocompromised patients.


Early treatment with five different mAb products was consistently linked with a reduced risk of hospitalization or death over a period of almost two years. Importantly, the continuous examination of mAb and non-mAb treatment therapies is necessary due to the rapid evolution of novel SARS-CoV-2 variants.

Journal reference:

  • Kip, K. E., McCreary, E. K., K., C., et al. (2023). Evolving Real-World Effectiveness of Monoclonal Antibodies for Treatment of COVID-19: A Cohort Study. Annals of Internal Medicine. doi:10.7326/M22-1286

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