MAPT and Alzheimer disease: Recent findings, however, suggest that pS199 and pS202 are not elevated in AD brains relative to healthy controls until much later stages of disease, such as Braak stage V/VI.45,46 These pathologically modified epitopes may appear too late in the disease process for successful therapeutic targeting which could explain the failure of our Qβ-AT8 vaccine to reduce tau pathology and rescue cognition.