The mouse monoclonal antibody is produced from a hybridoma resulting from fusion of SP2/0 myeloma and B-lymphocytes obtained from a mouse immunized with Spike RBD F (ab') 2. The antibody is specific against the Delta (B.1.617.2/AY.4) variant of SARS-CoV-2, and has no binding with the spike RBD of the wild type virus and the Alpha (B.1.1.7), Beta (B.1.351), Gamma (P.1), Omicron (B.1.1.529/BA.1) variant.