SA(rs)bc, or SARS-CoV-2 spike protein receptor-binding domain, is a crucial part of the virus that causes COVID-19. This domain allows the virus to attach to human cells by binding to the ACE2 receptor, facilitating infection. Understanding this interaction is vital for developing vaccines and treatments. Research on SA(rs)bc has led to the creation of various vaccines, including those from Pfizer-BioNTech and Moderna. These vaccines aim to stimulate the immune system to recognize and combat the virus effectively. By targeting the spike protein, they help prevent severe illness and reduce the spread of the virus.