Two clinical trials suggest that specific antibody treatments can prevent deaths and hospitalizations among people with mild or moderate COVID-19—particularly those who are at high risk of developing severe disease. The study results, both announced on 10 March, come from randomized, placebo-controlled, double-blind clinical trials, but have not yet been published. The resulting ‘monoclonal antibodies’ have since been tested in a variety of settings as treatments for COVID-19. Earlier in the pandemic, some key clinical trials involving people who had been hospitalized with COVID-19 found no benefit from monoclonal antibodies. The speed with which these monoclonal antibodies were developed holds a lesson for future pandemics, says Khoo.