Upon the outbreak of human cases of avian influenza virus(H7N9)infection in China since April 2013,the vaccine development was started soon after manufacturers received the vaccine strains.However,the development of such vaccines were delayed due to the unavailability of international reference reagents for HA quantification.NIFDC prepared the antiserum by immunization of sheep with recombinant HA protein,and the antigen references based on the previous experiences from 2009 A/H1N1,thus providing the manufacturers for SRID test.NIFDC also collaborated with Center for Biologics Evaluation,Health Canada to develop the Universal antibodies against Neuraminidase,which is the important surface antigen of influenza virus beside HA.The quantitative method was established for testing the NA content in seasonal influenza vaccines.