A composition comprising: an aqueous vehicle; and liposomes comprising (i) dimyristoylphosphatidylcholine ("DMPC"), (ii) dimyristoylphosphatidylglycerol ("DMPG"), or dimyristoyltrimethylammonium propane ("DMTAP"), or both DMPG and DMTAP, (iii) at least one sterol; and (iv) an antigenic polypeptide comprising a first polypeptide sequence comprising at least 10 contiguous residues of an influenza A M2 extracellular domain, the sequence of which has been modified to remove one or more cysteine residues naturally occurring in said M2 extracellular domain, and a second polypeptide sequence comprising a transmembrane sequence of, or derived from, a naturally occurring heterologous membrane protein, said second polypeptide sequence having a number of residues sufficient to cross a lipid bilayer, at least nine contiguous residues of which are predicted to form an alpha helix having a hydrophobicity score of 0.63 or greater, wherein the hydrophobicity score is calculated by the methodology of Eisenberg, wherein said first polypeptide sequence is coupled directly or indirectly to the Nor C- terminus of said second polypeptide sequence to provide an aqueous soluble fusion polypeptide, and wherein the antigenic polypeptide sequence of the fusion polypeptide is displayed on the outer surface of the liposomes. an aqueous vehicle; and liposomes comprising (i) dimyristoylphosphatidylcholine ("DMPC"), (ii) dimyristoylphosphatidylglycerol ("DMPG"), or dimyristoyltrimethylammonium propane ("DMTAP"), or both DMPG and DMTAP, (iii) at least one sterol; and (iv) an antigenic polypeptide comprising a first polypeptide sequence comprising at least 10 contiguous residues of an influenza A M2 extracellular domain, the sequence of which has been modified to remove one or more cysteine residues naturally occurring in said M2 extracellular domain, and a second polypeptide sequence comprising a transmembrane sequence of, or derived from, a naturally occurring heterologous membrane protein, said second polypeptide sequence having a number of residues sufficient to cross a lipid bilayer, at least nine contiguous residues of which are predicted to form an alpha helix having a hydrophobicity score of 0.63 or greater, wherein the hydrophobicity score is calculated by the methodology of Eisenberg, wherein said first polypeptide sequence is coupled directly or indirectly to the Nor C- terminus of said second polypeptide sequence to provide an aqueous soluble fusion polypeptide, and wherein the antigenic polypeptide sequence of the fusion polypeptide is displayed on the outer surface of the liposomes. (i) dimyristoylphosphatidylcholine ("DMPC"), (ii) dimyristoylphosphatidylglycerol ("DMPG"), or dimyristoyltrimethylammonium propane ("DMTAP"), or both DMPG and DMTAP, (iii) at least one sterol; and (iv) an antigenic polypeptide comprising a first polypeptide sequence comprising at least 10 contiguous residues of an influenza A M2 extracellular domain, the sequence of which has been modified to remove one or more cysteine residues naturally occurring in said M2 extracellular domain, and a second polypeptide sequence comprising a transmembrane sequence of, or derived from, a naturally occurring heterologous membrane protein, said second polypeptide sequence having a number of residues sufficient to cross a lipid bilayer, at least nine contiguous residues of which are predicted to form an alpha helix having a hydrophobicity score of 0.63 or greater, wherein the hydrophobicity score is calculated by the methodology of Eisenberg, wherein said first polypeptide sequence is coupled directly or indirectly to the Nor C- terminus of said second polypeptide sequence to provide an aqueous soluble fusion polypeptide, and wherein the antigenic polypeptide sequence of the fusion polypeptide is displayed on the outer surface of the liposomes.