Abstract: Disclosed herein are recombinant viruses and/or insect cells suitable for detecting the infection of a pathogen in a biological sample of a test subject. The information derived from the detection may also be used to render a diagnosis on whether the test subject is infected with the pathogen or not, so that proper course of treatment may be assigned to the subject. Also disclosed herein is a vaccine for the prophylaxis and/or treatment of infection caused by said pathogen.

Abstract: Provided is a chimeric hemagglutinin (HA) protein including an HA1 subunit and an HA2 subunit, in which the HA1 subunit is composed of a first domain derived from a parental HA1 subunit of a first subtype influenza virus and a second domain derived from a parental HA1 subunit of a second subtype influenza virus. The chimeric HA protein has improved thermal stability and can be used in a vaccine composition for preventing influenza virus infection. Also provided is a method of inducing an immune response against an influenza virus in a subject in need thereof that includes administering the chimeric HA protein to the subject, thereby conferring protection against the influenza virus infection on the subject.