A human that ingests the blood of a vampire does not become a vampire but rather an incomplete vampire. The only known incomplete vampire in the series is Mikaela Hyakuya. Newly-turned vampires can survive off of the blood of the one how sired them, but this will only work for a limited period of time.
Incomplete vampires retain their human eye colors but grows fangs and grow in strength. Whether or not their ears grow pointed like a true vampires is unknown. Unlike true vampires, they continue aging until drinking human blood until becoming true vampires.
An incomplete vampire has no heart beat.
Despite incomplete vampires not being true vampires, true vampires seem to have no aversion towards them. Mika is seen alongside them several times, and they seem unperturbed by the prospect of an incomplete vampire working with them.