National Influenza Centres (NICs) collect virus specimens in their country and perform preliminary analysis. They ship representative clinical specimens and isolated viruses to WHO CCs for advanced antigenic and genetic analysis. The results form the basis for WHO recommendations on the composition of influenza vaccine each year, as well as relevant risk assessment activities of WHO. NICs are national institutions designated by national Ministries of Health and recognized by WHO. They form the backbone of the WHO’s Global Influenza Surveillance and Response System (GISRS).