The physics case of the International Linear Collider (ILC) is intended to encompass detailed studies of the Higgs boson and top-quark sectors as well as of fermion-pair production, complemented with direct searches for BSM physics manifestations. All these components of the physics programme involve flavour specific dynamical content, which calls for unprecedented performances of the charged particle detectors composing the experiments, special attention being devoted to the possibility to achieve ambitious flavour tagging performances. The latter benefit from the moderate radiation tolerance and read-out speed required, combined with the possibility to exploit the machine duty cycle for power saving, to achieve thereby a spatial resolution per detector layer of a few micrometres in both directions, combined with a material budget not exceeding
0.15 % of radiation length.
Since the delivery of the ILC TDR IN 2012/13, substantial progress was achieved to develop a vertex detector fully suited to the physics requirements. Several pixel sensor approaches were
followed, both from the technological and from the read-out architecture points of view. They are motivated by the capability to suppress the impact of beam related background, which dominates the hit density of the vertex detector, and tends to grow as the luminosity of the ILC is being upgraded to 4 to 6 times the TDR values. The paper summarises the performances achieved as well as the status and the perspectives of the different approaches. It will show that the possibility
opens up to realise single bunch tagging with square pixels featuring less than 20¸tm pitch and associated to a power consumption compatible with air cooling.