The ruling to Wayta reads:
(11/10/2023)
Wayta, Trainer Prodigy's last ability affects only triggered abilities whose trigger conditions refer specifically to damage being dealt, such as the ability granted by Mephidross Vampire or the last ability of Wrathful Raptors. "

Mephidross vampire does not have a triggered ability that triggers of damage being dealt.

It has "Each creature you control is a Vampire in addition to its other creature types and has "Whenever this creature deals damage to a creature, put a +1/+1 counter on this creature.""

This triggers of dealing damage, not receiving damage.