YSO Variability as seen with VVV and UKIDSS

The VISTA Variables in the Via Lactea Survey (VVV) provides a 5 year time series of 2 micron photometry for YSOs across a large part of the Galactic plane. This, along with the two-epochs of UKIDSS GPS data in the north, has provided the first large samples of highly variable YSOs (Delta K = 1 to 5 mag). The observed variability probes processes in the inner accretion disc that cause changes in accretion rate or variable extinction. Gravitational instabilities on larger scales may also be involved. We present new results, including a much enlarged sample of YSOs with Delta K above 3 mag. We also introduce the ongoing VVVX extension to VVV.