"very vast" is a correct and usable phrase in written English.
You can use it to emphasize the large size of something. For example, "The sky was very vast and filled with stars."
"He didn't have a very vast friend group".
It's very vast, I was starving by the time I finished seeing everything.
The application of this research extends well beyond sustainability considerations to the very vast area of optimum design with multi criteria.
And when you have a landscape that is very vast and inaccessible, it makes it very difficult to find these snakes.
"The difference between not caring what your 'enemy party' thinks of you and caring about how you affect people whose values line up with yours is very vast".
And, like the very vast majority of women in Yemen, Ms. Samawi covers her face when she goes out in public.
The Islamic State is a formidable fighting force that conquered very quickly vast areas of Iraq and Syria.
In addition, building technologies nowadays are integrated and containing many disciplines in the same time, and each discipline is dependent on the other disciplines in a very complex vast connections.
We were watching something very sophisticated: vast marionettes, giant articulated dolls manipulated with exquisite delicacy (the turn of the girl's wrist, the snaking reach of the camel's trunk).
Before very long vast stockpiles of 'recovered' sulphur were building up on the plains of Alberta, Canada.
But even when voters seem very unhappy, the vast majority of incumbents in both parties are reelected.
