This is an open-labeled randomised-controlled trial (RCT) investigating the safety and therapeutic efficacy of oral VitA in combination with ST for patients suffering from prolonged COVID-19-related OD.~Prior to the initiation of treatment, all patients will receive subjective and objective olfactory assessments. Comprehensive ear, nose, and throat (ENT) examination will be performed to rule out alternative causes of OD. All participants will receive resting-state functional magnetic resonance imaging (rs-fMRI) of the brain before treatment as baseline evaluation.~Patients with prolonged COVID-19-related OD will be assigned to the intervention (group A or B) or control (group C) arms:~Intervention arm A. 14-day course of daily oral VitA 7500µg RAE (retinol activity equivalents) in combination with ST three times per day for 4 weeks; or B. ST three times per day for 4 weeks alone; or~Control arm C. Observation~In addition, healthy controls who were tested negative for SARS-CoV-2 by reverse transcription polymerase chain reaction (RT-PCR) will receive rs-fMRI brain scans for radiological comparisons.~At the completion of the trial, subjective and objective olfactory assessments will be repeated to document clinical changes in olfaction. Follow-up rs-fMRI will be performed to document neuroradiological changes in the brain structures and cerebral network functional connectivity (FC).
A combination of oral vitamin A (VitA) and intense aromatic chemosensory smell training (ST) by pulse aromatic stimulation will expedite the neurosensory recovery of olfaction in patients suffering from prolonged COVID-19-related olfactory dysfunction (OD).