The National Institutes of Health (NIH) COVID-19 Treatment Guidelines have been updated to include new recommendations on the use of anti-SARS-CoV-2 monoclonal antibodies in outpatients with mild to moderate COVID-19 who are at high risk of disease progression.

Based on the available evidence related to the SARS-CoV-2 variants, the panel now recommends using 1 of the following combination therapies for treatment of eligible patients as outlined in the Emergency Use Authorizations (EUA) for these products:

Treatment with anti-SARS-CoV-2 monoclonal antibodies should be initiated as soon as possible after a positive result on a SARS-CoV-2 antigen or nucleic acid amplification test is confirmed and within 10 days of symptom onset. At this time, there are no comparative data to determine whether one combination therapy is safer or more effective.

While the clinical impact is not fully known, there are certain SARS-CoV-2 variants, such as those that contain the E484K mutation, which may reduce the virus’ susceptibility to these therapies, particularly bamlanivimab and to a lesser extent casirivimab and etesevimab.  Based on these reports, some of the NIH panel members recommended the use of casirivimab plus imdevimab in regions where SARS-CoV-2 variants with reduced in vitro susceptibility to bamlanivimab plus etesevimab is common. However, they noted that in vitro susceptibility data may not necessarily correlate with clinical outcomes.

Given the concerns regarding decreased susceptibility of SARS-CoV-2 variants, the panel recommends against the use of bamlanivimab monotherapy (Recommendation: Strong; Evidence rating: Expert opinion), unless combination therapies are unavailable. In these circumstances, monotherapy with bamlanivimab should be considered on a case-by-case basis.

The panel also recommends against the use of the monoclonal antibody therapy in hospitalized patients unless part of a clinical trial (Recommendation: Strong; Evidence rating: Other randomized trials or subgroup analyses of randomized trials), or if the treatment is being considered for patients with mild to moderate COVID-19 hospitalized for other reasons and who meet the EUA criteria.

Additional information explaining the rationale for these recommendations can be found here.


National Institutes of Health. NIH: COVID-19 Treatment Guidelines. Updated April 8, 2021. Accessed April 9, 2021.