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REGEN-COV prevents Covid-19: findings from a novel study. Image credit: Getty images

REGEN-COV prevents Covid-19: findings from a novel study.

In a novel study conducted by Meagan P. O’Brien and colleagues who subsequently published the data in the New England Journal of Medicine, subcutaneous REGEN-COV prevented Covid-19 (both symptomatic and asymptomatic disease) in uninfected household contacts of infected persons. Among those with SARS-CoV-2 infection, the REGEN-COV recipients recovered faster than the placebo recipients.

REGEN-COV is a combination of two monoclonal antibodies – casirivimab and imdevimab. Regeneron Pharmaceuticals manufactures this combination therapy. The two monoclonal antibodies neutralise the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) through their interaction with the spike protein that the virus uses to enter the host cells. The combination therapy protects against SARS-CoV-2 and all the variants of concern. They include the alpha, beta, delta, epsilon, and gamma variants. Studies have shown that with REGEN-COV, the incidence of hospitalisation or death among outpatients with Covid-19 reduces by about 70%.

With such an impressive statistic, Meagan P. O. et al. dared to understand if REGEN-COV could prevent SARS-CoV-2 infection and Covid-19 in persons at a high risk of the disease due to exposure to a person with Covid-19 within the same household. They recruited participants who were 12 years or older and had no active or previous SARS-CoV-2 infection within four days after a household contact had attained a Covid-19 diagnosis. The participants then received a subcutaneous injection of 1200mg of REGEN-COV (600mg of each of the two monoclonal antibodies) or matching placebo in a 1:1 ratio. The result was to primarily ascertain the number of those who would get SARS-CoV-2 infection. They were 1505 participants who took part in the study: 753 in the REGEN-COV group and 752 in the placebo group.


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Upon data analysis, 11 and 59 participants from the REGEN-COV and placebo groups, respectively, developed symptomatic Covid-19. Among those with symptomatic infection, participants in the REGEN-COV group recovered two weeks earlier than those in the placebo group in terms of symptom resolution. The former also had a shorter duration of a high viral load than the latter by 0.9 weeks. All participants tolerated the interventions well.

The results of this study are fascinating for several reasons. First, the monoclonal antibodies have proven efficacy against all the Covid-19 variants of concern, a feat that we require from all preventive therapies, vaccines inclusive. Second, REGEN-COV through a subcutaneous injection provides a safe yet effective option to prevent Covid-19 among household contacts to infected persons instead of relying only on standard operating procedures like masks, social distancing, and hand hygiene. In the wake of waning immunity among vaccine recipients and the anti-vaxxers, REGEN-COV is a viable option for their continued protection. Because it is a subcutaneous injection, the combination therapy requires few consumables that almost anyone can access within the society. It can be safely administered from home or in an outpatient setting, just like vaccines. The downside of preventive therapy is, and will always be its high price tag.

For more details about this study, visit


MBChB (MUK), Graduate Fellow, Department of Physiology, Makerere University Founder and Content Creator Peer reviewer, Associate Editor

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