Influenza virus vaccine and uses thereof

A polypeptide comprising:

• a. an influenza hemagglutinin HA1 domain that comprises an HA1 N-terminal stem segment covalently linked to a linker of 1 to 50 heterologous residues that is in turn covalently linked to an HA1 C-terminal short stem segment;
• said HA1 domain in tertiary or quaternary association with
• b. an influenza hemagglutinin HA2 domain;
• wherein the HA1 N-terminal stem segment consists of amino acid residues corresponding approximately to amino acids HA1N-term through Ap of an HA1 domain and the HA1 C-terminal short stem segment consists of amino acid residues corresponding approximately to amino acids Bq through HA1C-term of an HA1 domain, wherein HA1N-term is the N-terminal amino acid of the HA1 domain, wherein HA1C-term is the C-terminal amino acid of the HA1 domain, wherein Ap is Cys that corresponds to amino acid position 52 of an HA1 using H3 numbering, wherein Bq is Cys that corresponds to amino acid position 305 of an HA1 using H3 numbering, and wherein the polypeptide lacks an influenza virus hemagglutinin globular head domain.