REGEN-COV antibody combination to prevent COVID-19 severity

A recent study posted to the Research Square* preprint server, and currently under consideration at a Nature Portfolio Journal, assessed the effectiveness of REGEN-COV, a combination of casirivimab and imdevimab monoclonal antibodies, in the prevention of coronavirus disease 2019 (COVID-19) disease severity.

Study: Effectiveness of REGEN-COV Antibody Combination in Preventing Severe COVID-19 Outcomes. Image Credit: Terelyuk/Shutterstock

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines and their efficacy have played a crucial role in curbing the morbidity and mortality caused by COVID-19. However, in the wake of breakthrough infections and reports of waning vaccine efficiency, treatment methods that can effectively prevent the severity of disease in infected patients are vital.

About the study

The present retrospective cohort study investigated the effectiveness of REGEN-COV in the prevention of hospitalization caused by the SARS-CoV-2 Delta variant of concern and related disease severity and death.

Data was collected from the database of Clalit Health Services (CHS), a healthcare organization in Israel. The eligible participants were of ages 12 years and older, had tested SARS-CoV-2 polymerase chain reaction (PCR) positive for the first time, were at a higher risk of developing severe COVID-19, and were a member of CHS for a year as of the day of infection.

The study was conducted on two groups: one group containing treated patients who had tested PCR positive for the first time between 19 September 2021 and 8 December 2021 and were treated with REGEN-COV and the second group with untreated patients with a first positive result of a PCR test between 1 July 2021 and 8 December 2021 and did not receive REGEN-COV.

Each treated patient was matched with untreated patients based on age, sector of the population, gender, socioeconomic status, body mass index (BMI), the status of immunosuppression, pregnancy, and the date of first vaccination dose. The date when the REGEN-COV treatment began for the treated patients was considered the index date while the index date for an untreated patient was based on the duration between the diagnosis and administration of REGEN-COV of the matched treated patient. A secondary analysis was also conducted on patients of the age group younger than 60 years and those 60 years or older.

Three outcomes of the study were examined: the number of COVID-19-related hospitalizations, patients suffering from severe COVID-19, and COVID-19-related death.  


The study results showed that a total of 162,795 CHS members tested COVID-19 positive between 1 July 2021 and 8 December 2021, out of which 135,458 members were eligible for the present study. Among the eligible participants, 289 were treated with REGEN-COV, and 1,294 were untreated. The median age of the patients selected was 67 years with 49% of the patients being male.

In the REGEN-COV-treated group, the risk of COVID-19-related hospitalization was reduced by 55.2% while the risk of COVID-19 severity lowered by 59.4%, and the risk of death due to COVID-19 decreased by 93.8%.

The secondary analysis indicated that the risk of COVID-19-related hospitalization in treated patients of ages 60 years or older was reduced by 55.3%, risk of disease severity was lowered by 61.5%, and risk of death caused by COVID-19 decreased by 95.0%. In patients of ages below 60 years, the risk of COVID-19-related hospitalization was lowered by 91.5% while COVID-19 severity and related death were rare in this age group.  


The study findings showed that REGEN-COV was fairly efficient in preventing COVID-19-related hospitalizations as well as reducing disease severity and related death in patients infected with the SARS-CoV-2 Delta variant.

The researchers believe that amid reports of breakthrough infections and reduction in vaccine efficacy against newly emerging variants of the virus, treatment agents like REGEN-COV can control further extension of the pandemic.

*Important notice

Research Square* publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
  • Samah Hayek, Yatir Ben-Shlomo, Noa Dagan et al. (2022). Effectiveness of REGEN-COV Antibody Combination in Preventing Severe COVID-19 Outcomes. Research Squaredoi:

Posted in: Medical Research News | Medical Condition News | Disease/Infection News

Tags: Antibodies, Body Mass Index, Coronavirus, Coronavirus Disease COVID-19, covid-19, Efficacy, Healthcare, Immunosuppression, Mortality, Pandemic, Polymerase, Polymerase Chain Reaction, Pregnancy, Protein, Research, Respiratory, SARS, SARS-CoV-2, Severe Acute Respiratory, Severe Acute Respiratory Syndrome, Spike Protein, Syndrome, Vaccine, Virus

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Written by

Susha Cheriyedath

Susha has a Bachelor of Science (B.Sc.) degree in Chemistry and Master of Science (M.Sc) degree in Biochemistry from the University of Calicut, India. She always had a keen interest in medical and health science. As part of her masters degree, she specialized in Biochemistry, with an emphasis on Microbiology, Physiology, Biotechnology, and Nutrition. In her spare time, she loves to cook up a storm in the kitchen with her super-messy baking experiments.

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