Monoclonal Antibodies Reduce Mortality in COVID-19 Independent of Vaccination

Both casirivimab-imdevimab and sotrovimab reduced the risk of COVID-19-related mortality indepedent of vaccination status and were most effective when administered within 5 days of infection onset.

Monoclonal antibody (mAb) treatment with casirivimab-imdevimab vs sotrovimab are similar in their effectiveness against mild to moderate COVID-19 infection, as both reduce the risk of mortality and hospitalization independent of vaccination status. These study results were published in the International Journal of Infectious Diseases.

Researchers conducted a prospective study at 2 COVID-19 centers in Naples, Italy between July 2021 and May 2022. Eligible patients (n= 1,026) were those diagnosed with mild to moderate COVID-19 within the previous 10 days who were at risk for progressing to severe disease. All patients were referred for mAb treatment by a primary care physician, and outcomes were compared between those who received casirivimab-imdevimab (1200/1200 mg) vs sotrovimab (500 mg). Assessed outcomes included 60-day mortality, time to SARS-CoV-2 clearance, hospitalization, and the need for supplemental oxygen. Multivariable logistic regression models were used to assess the effect of clinical variables on the risk of mortality.

A total of 1026 patients were included in the analysis, of whom 60.2% received casirivimab-imdevimab and 39.8% received sotrovimab. The mean (SD) patient age was 63 (16.9) years, 52.4% were men, and the median time from COVID-19 onset to mAb treatment initiation was 3 (IQR, 2-5) days. In addition, the majority of patients were vaccinated (78.1%), the median time from receipt of the last vaccine dose to mAb initiation was 5 (IQR, 3-6) months, and the median number of comorbidities was 2 (IQR, 1-3).

At the time of mAb initiation, 271 (26.4%) and 170 (16.5%) patients were receiving concomitant treatment with corticosteroids or low-molecular-weight heparin, respectively.

[T]he emergence of new SARS-CoV-2 variants renders current mAbs ineffective and new therapies are needed

The 60-day mortality rate did not significantly differ between patients who received casirivimab-imdevimab vs sotrovimab (1.94% vs 2.28%; P =.582). There also were no significant between-group differences in the rate of hospitalization, though patients who received sotrovimab were significantly less likely to require supplemental oxygen (P <.005).

Of note, initiation of mAb treatment within the first 5 days of infection onset was associated with significantly decreased risk of mortality.

Further analysis showed that the rate of mortality did not significantly differ between vaccinated vs unvaccinated patients in both groups. However, vaccinated vs unvaccinated patients had significantly decreased risk for hospitalization (3.2% vs 7.6%; P <.005) and for requiring supplemental oxygen (7.5% vs 17.3%; P <.0001), as well as significantly shorter times to SARS-CoV-2 viral clearance (median, 13 vs 17 days; P <.0001).

The researchers found that 60-day mortality rates were higher among patients who were vs were not receiving concomitant corticosteroids at the time of mAb initiation (4.3% vs 1.28%).

Significant factors associated with increased risk of mortality included advanced age (>70 years; P <.001), active hematologic malignancy, kidney insufficiency (P <.041), and the need for supplemental oxygen (P <.001).

Limitations of this study include the relatively small number of observed outcomes and the lack of a control group.

Despite these findings, “[T]he emergence of new SARS-CoV-2 variants renders current mAbs ineffective and new therapies are needed,” the researchers concluded.