Will slits and scarring damage vellus hairs during a hair transplant?

There are usually vellus hairs in bald areas on the head. Are these vellus hairs damaged when making the slits on the recipient area for the hair transplant? How deep do the slits go, and how deep are the bulbs of tiny vellus hair? If a person has done a hair transplant and begins using finasteride and microneedling where he has transplanted hair, can new hair grow, or is that area damaged with scar making it impossible for new hairs to grow?