Enzyme ImmunoAssay (ELISA) for the determination of IgG antibodies to groups ACWY Meningococcus in human plasma and sera. The product is intended for the follow-up of patients administered with a meningococcal vaccine, containing the polysaccharides from groups A, C, Y and W135. Micro-plates are coated with a preparation of purified capsular polysaccharides formed by serogroups A, B, C, Y and W135. In the 1st incubation, the solid phase is treated with diluted samples and anti-Meningococcus IgG are captured, if present, by the antigens.After washing out all the other components of the sample, in the 2nd incubation bound anti-Men IgG are detected by the addition of anti hIgG antibody, labeled with peroxidase (HRP). The enzyme captured on the solid phase, acting on the substrate/chromogen mixture, generates an optical signal that is proportional to the amount of anti-Men IgG antibodies present in the sample. A cut-off value permits to transform the optical density values detected in positive or negative results due to the presence of absence of anti-Men IgG.