The SARS-CoV-2 (Omicron BA.5) Spike S1 subunit with His Tag is used in vaccine development and diagnostic assays to detect immune responses against the Omicron BA.5 variant of SARS-CoV-2. It serves as a key antigen for studying neutralizing antibodies and T-cell responses. It enables research on viral entry mechanisms and host cell receptor interactions. It supports evaluation of vaccine efficacy and therapeutic antibody development. It is widely applied in ELISA, lateral flow assays, and structural studies due to its high purity and proper conformation.