Critical appraisal of: "expression of SARS-CoV-2 spike protein in cerebral arteries: implications for hemorrhagic stroke post-mRNA vaccination".

This correspondence offers a critical appraisal of the study by Ota et al. on the expression of SARS-CoV-2 spike protein in cerebral arteries following mRNA vaccination. While the original study contributes to understanding potential neurological sequelae post-vaccination, we identify several methodological limitations. Chief concerns include the absence of a control group, reliance on negative nucleocapsid staining to exclude prior infection, a small and unbalanced sample size, lack of lesionspecific tissue analysis, and unconfirmed RNA detection techniques. These issues collectively undermine causal inferences regarding vaccine-related spike protein persistence. We recommend methodological refinements for future studies, including matched controls, serial serological testing, tissue validation protocols, and robust subgroup stratification.