An immunogenic polypeptide for use in inducing an immune response against Plasmodium infection comprises an amino acid sequence corresponding to a non-full length fragment of the apical membrane antigen 1 (AMA-1) of Plasmodium species which does not include a transmembrane domain thereof, and which is stabilised by folding thereof. Production of the immunogenic polypeptide by expression of a recombinant DNA molecule in a host cell, and methods and compositions using the immunogenic polypeptide are disclosed.
