The invention relates to an immunogenic complex comprising a polymerised antigen, mannan and a dialdehyde, to the composition containing same, and to the use thereof as a stimulator of the immune response and a vaccine, useful in the treatment of infectious diseases, neoplasia and allergies. The invention also relates to the method for producing said immunogenic complex, based on the simultaneous polymerisation and conjugation of the antigen and the mannan by means of the use of a dialdehyde.