pf2e.fyi
From Pathfinder Lost Omens Ancestry Guide, which isn't enabled.

Inoculation Subroutine

FEAT 5

Your nanites reject diseases with ease. Each time you succeed at a Fortitude save against an ongoing disease, you reduce its stage by 2, or by 1 against a virulent disease. Each critical success you achieve against an ongoing disease reduces its stage by 3, or by 2 against a virulent disease.

Pathfinder Lost Omens Ancestry GuideOGL