Illustration of two different therapeutic monoclonal antibodies (y-shaped) binding to different antigenic sites on a SARS-CoV-2 virus spike protein (red). SARS-CoV-2 causes the respiratory disease Covid-19. Antibodies are proteins of the immune system that bind to specific antigens, such as a viral protein, and either mark the pathogen for destruction by other immune cells, or destroy it themselves. Cocktails of antibodies have been shown to be effective against SARS-CoV-2 variants that are able to evade the immune response.