Passive immune therapies: another tool against COVID-19.
Passive immune therapy consists of several different therapies, convalescent plasma, hyperimmune globulin, and severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralizing monoclonal antibodies. Although these treatments were not part of any pandemic planning prior to coronavirus disease 2019 (COVID-19), due to the absence of high-quality evidence demonstrating benefit in other severe respiratory infections, a large amount of research has now been performed to demonstrate their benefit or lack of benefit in different patient groups. This review summarizes the evidence up to July 2021 on their use and also when they should not be used or when additional data are required. Vaccination against SARS-CoV-2 is the most important method of preventing severe and fatal COVID-19 in people who have an intact immune system. Passive immune therapy should only be considered for patients at high risk of severe or fatal COVID-19. The only therapy that has received full regulatory approval is the casirivimab/imdevimab monoclonal cocktail; all other treatments are being used under emergency use authorizations. In Japan, it has been licensed to treat patients with mild to moderate COVID-19, and in the United Kingdom, it has also been licensed to prevent infection.