This phylogenetic tree shows the genetic relationships between representative haemagglutinin genes of A(H3N2) viruses received by the Centre in 2014. As seen in this figure, the majority of A(H3N2) viruses are in clades 3C.2 and 3C.3. The recommended vaccine strain, A/Switzerland/9715293/2013, is in subclade 3C.3a.