Influenza virus vaccines and uses thereof

A method of immunizing a subject against an influenza virus, comprising:

• I. (a) administering to the subject an effective amount of a first immunogenic composition comprising a first inactivated and split influenza A virus, wherein the a first inactivated and split influenza A virus comprises a first influenza virus chimeric hemagglutinin (HA) polypeptide, wherein the first influenza A virus chimeric HA polypeptide comprises an influenza A virus HA stem domain and an influenza virus HA globular head domain, wherein the influenza A virus HA globular head domain is heterologous to the influenza A virus HA stem domain;
• and
• (b) subsequent to the administration of the first immunogenic composition to the subject, administering to the subject an effective amount of a second immunogenic composition comprising a second inactivated and split influenza A virus, wherein the a second inactivated and split influenza A virus comprises a second chimeric influenza virus HA polypeptide, wherein the second influenza virus chimeric HA polypeptide comprises the HA stem domain of influenza virus A/California/4/2009 (H1N1) HA and the HA globular head domain of influenza virus A/Vietnam/1203/2004 (H5) HA, and
• wherein the HA globular head domain of the first chimeric influenza virus HA polypeptide is different than the HA globular head domain of the second chimeric influenza virus HA polypeptide;
• or
• II. (a) administering to the subject an effective amount of a second immunogenic composition comprising a second inactivated and split influenza A virus, wherein the a second inactivated and split influenza A virus comprises a second chimeric influenza virus HA polypeptide, wherein the second influenza virus chimeric HA polypeptide comprises the stem domain of influenza virus A/California/4/2009 (H1N1) HA and the globular head domain of influenza virus A/Vietnam/1203/2004 (H5) HA;
• and
• (b) subsequent to the administration of the second immunogenic composition to the subject, administering to the subject an effective amount of a first immunogenic composition comprising a first inactivated and split influenza A virus, wherein the a first inactivated and split influenza A virus comprises a first influenza virus chimeric hemagglutinin (HA) polypeptide, wherein the first influenza A virus chimeric HA polypeptide comprises an influenza A virus HA stem domain and an influenza virus HA globular head domain, wherein the influenza A virus HA globular head domain is heterologous to the influenza A virus HA stem domain, and
• wherein the HA globular head domain of the first chimeric influenza virus HA polypeptide is different than the HA globular head domain of the second chimeric influenza virus HA polypeptide.