In this prospective monocentric study, we report low hospitalization and mortality rates with the use of casirivimab plus indevimab combination for mild to moderate COVID-19 infection in real-life clinical practice, during a massive COVID wave due to the Delta variant in a predominantly unvaccinated Afro-Caribbean population.
The main limitation of our study is that there is no control group, and it is therefore difficult to ensure the benefit of the treatment. Nevertheless, comparison with the other available data suggest it strongly.
Weinreich et al found in their clinical trial a hospitalization rate as low as 1%, but mean age was 48 years and main reason for treatment was obesity [5]. Others found in real-life setting similar hospitalization rate to our data (6%), but lower mortality (0.6%): here again, mean age was lower (59 years) and only 30% of patients had comorbidities [7]. Thus, our results can be explained by a more vulnerable population with older and more comorbid patients. Another explanation for our results could be the higher virulence of the Delta variant, leading more frequently to hospitalizations than previous variants of concern [9]. To our knowledge, no efficiency data of NmAbs on Delta variant have been published until now.
On the other hand, the outcomes of the “casirivimab plus indevimab French cohort” show hospitalization rates over 20% and mortality rates over 5%, which is much higher than our data, but in a population with 65% of patients being immunosuppressed [10]. Similarly, mortality rates in solid organ transplants reported in the literature range form 13 to over 30% [11], while we only had one death among our 13 transplanted patients (8%). Thus, even if we don’t have a control group, all these data suggest a benefit of treating with NmAbs high-risk patients infected with the Delta variant of Covid-19 not requiring supplemental oxygen, to avoid hospitalization and deaths, which is particularly important in Covid waves overwhelming hospital capacities.
When analyzing the predictive factors for treatment failure, older age was logically associated with poor outcome [7], but we also found an association with the presence of dyspnea experienced by the patient (without lowering the saturation < 94%). To our knowledge, this has never been reported in the literature, and probably reflects a greater respiratory involvement. Unlike others, we haven’t found any correlation with duration of symptoms before infusion [7, 8].
This study illustrates the feasibility of creating rapidly a Hospital Day Unit with a dedicated and specialized medical team, allowing to treat with intravenous treatments several patients per day at an early stage of the disease. It also shows the possibility to spread quickly and effectively the information of a new therapeutic strategy to the medical community. We can consider our strategy highly effective as only 277 patients were treated during the same study period with NmAbs in France [10], while 217 cases were treated on our much smaller territory. This suggests a high catchup of COVID patients targeted by NmAbs when we know that 1576 patients were admitted to our emergency department during that period.
In summary, our data highly suggest benefit of casirivimab plus indevimab combination in mild to moderate Covid-19 due to Delta variant in high-risk patients to avoid oxygen request, hospitalization, and deaths. This should incite to the rapid dissemination of medical information on new therapeutic tools and to the creation of dedicated ambulatory units.