SARS-CoV-2 vaccination and chemosensory dysfunction after COVID-19

Olfactory and taste dysfunction are common symptoms of COVID-19 and post-acute COVID-19 syndrome, yet the effects of COVID-19 vaccines on chemosensory perception remain incompletely understood. This global, multilingual, online survey assessed post-vaccination changes in chemosensory function among individuals with and without COVID-19-related chemosensory impairment. Between May 2022 and August 2023, 2,955 responses were collected via convenience sampling, of which 1,352 were included in the analyses. Participants reported vaccination status, side effects, and chemosensory function before and after each vaccine dose. Pfizer-BioNTech accounted for 46.2% of doses, followed by Sputnik V (16.3%), Moderna (15.4%), AstraZeneca (8.9%), and Sinopharm (7.4%). More than 90% of participants reported no change in their general sense of smell or taste following vaccination, regardless of pre-existing chemosensory impairment. Among participants with qualitative chemosensory distortions (one-third of the sample), improvement was reported by 11-18% for parosmia, 20-29% for phantosmia, and 12-21% for taste distortion, depending on the vaccine dose, while worsening was reported by 3% or fewer. Side effects varied by vaccine type and were more frequent among individuals with worsened chemosensory symptoms. These findings suggest that COVID-19 vaccination is unlikely to adversely affect chemosensory function for most individuals. Given the observational design and reliance on self-reported data, the results should be interpreted cautiously. Future longitudinal studies using objective measures are needed to clarify these associations.