The first are patients with non-severe Covid-19 who are at the highest risk of hospitalisation and the second are those with severe or critical Covid-19 who are seronegative, meaning they have not mounted their own antibody response to Covid-19, the WHO Guideline Development Group (GDG) panel of international experts and patients wrote in The BMJ.
The GDG panel, however, urged drug producing companies and governments to address the high price and limited production of the antibody combination and ensure safe and appropriate handling of the medicine.
Casirivimab and imdevimab are monoclonal antibodies that when used together bind to the SARS-CoV-2 spike protein, neutralising the virus's ability to infect cells.
The first recommendation for non-severe Covid patients is based on new evidence from three trials that have not yet been peer reviewed, but show that casirivimab and imdevimab probably reduce the risk of hospitalisation and duration of symptoms in those at highest risk of severe disease, such as unvaccinated, older, or immunosuppressed patients.
The second recommendation critical Covid patients is based on data from the a trial which showed that casirivimab and imdevimab probably reduce deaths (ranging from 49 fewer per 1,000 in the severely ill to 87 fewer in the critically ill) and the need for mechanical ventilation in seronegative patients.
For all other Covid-19 patients, any benefits of this antibody treatment are unlikely to be meaningful, the experts wrote.
The panel also acknowledged several cost and resource implications associated with this treatment, which may make access to low and middle income countries challenging. For example, rapid serological tests will be needed to identify eligible patients who are severely ill, treatment must be given intravenously using specialist equipment, and patients should be monitored for allergic reactions.
They also recognised the possibility that new variants may emerge in which casirivimab and imdevimab antibodies may have reduced effect.
However, they say given the demonstrated benefits for patients, "the recommendations should provide a stimulus to engage all possible mechanisms to improve global access to the intervention and associated testing."