Used in vaccine development and therapeutic research targeting the Omicron BA.2.75 variant of SARS-CoV-2. The Fc-tagged spike receptor-binding domain serves as a key antigen in immunoassays to measure neutralizing antibody responses in patient sera or after vaccination. It is also employed in binding studies to evaluate the efficacy of monoclonal antibodies and antiviral drugs. Due to the Fc tag, it can be easily detected and purified using standard anti-Fc reagents, making it valuable in high-throughput screening and diagnostic applications. Additionally, it supports structural studies to understand viral entry mechanisms and immune evasion properties of the variant.