Critical appraisal of methodological rigor in a systematic review on post-COVID-19 vaccination-associated olfactory dysfunction

We read with keen interest the article by Kawabata et al. titled "Olfactory disorder after COVID-19 vaccination," which explores 16 cases of olfactory dysfunction temporally associated with vaccination (1). The paper addresses an important and under-recognized topic; however, several methodological aspects warrant clarification to aid accurate interpretation. First, the inclusion of five institutional cases within a review otherwise presented as PRISMA-compliant raises questions regarding methodological consistency. Under PRISMA, all included studies should be identified through transparent and reproducible database searches (2). Clarifying whether institutional data were processed separately from literature-derived cases would strengthen transparency and avoid confusion about the evidence level.