Yes. You have two options: External Video and NDI.
vMix External Video (virtual camera)
First, make sure that "vMix Video / Streaming" is checked in the vMix settings.
Note: in order to support vertical 1080p (720x1280) in Loola, set the output height in vMix to be equal or larger than 1280:
Next, click the "External" button in vMix:
Next, select vMix in Loola and set desired resolution:
Note: the integral vMix Virtual Camera driver support video only. To get audio out of vMix, see the NDI option below.
vMix and NDI:
The video/audio flow: vMix --> NDI --> Loola --> Social Platforms
Start by with enabling NDI output in vMix:
More details here:
Next, run the NDI Virtual Input:
Next, configure NDI to show the vMix output.
Next, select NDI audio and video sources in Loola: