The APOLLO Trial: A Proof-of-Concept Study for Vitamin A Nasal Drops in COVID-19 Related Post-Infectious Olfactory Dysfunction

Yeap, Z., Sobhan, R., Bengtsson, S., Sami, S., Clark, A., Vishwakarma, R, Boardman, J, High, J, Klyvyte, G, Ergisi, M, Hummel, T and Philpott, C. M. (2026) The APOLLO Trial: A Proof-of-Concept Study for Vitamin A Nasal Drops in COVID-19 Related Post-Infectious Olfactory Dysfunction. Chemical Senses. ISSN 0379-864X

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Abstract

Post-infectious olfactory dysfunction (PIOD) is common in COVID-19 patients. This two-arm double-blinded randomised controlled trial aimed to establish proof-of-concept for Vitamin A versus placebo as a treatment modality for patients with PIOD. This study compared 9000 IU daily self-administered vitamin A intranasal drops versus peanut oil drops over 12 weeks in COVID-19 patients with PIOD. Outcome measures included: olfactory bulb volume (OBV), olfactory sulcus depth, cerebral functional MRI Blood Oxygen Level Dependent (BOLD) signal, Sniffin’ Sticks TDI score, SSParoT, Olfactory Disorder Questionnaire (ODQ) score and Brain Derived Neurotropic Factor (BDNF) levels were collected from participants at baseline and after trial intervention at 12 weeks. Fifty-seven PIOD were recruited in the trial and allocated to Vitamin A or placebo arm at a 2:1 ratio. After withdrawals and exclusions, 30 participants in the Vitamin A arm and 15 in the placebo arm were analysed. There was no significant difference in the change in OBV between both groups. Aside from an improvement in quality-of-life component of ODQ questionnaire scores (p = 0.01), there were no significant differences in any of the other secondary outcome measures. This proof-of-concept trial has demonstrated no significant effect of intranasal Vitamin A on olfactory function in COVID-19 PIOD patients. Further work is required to identify other therapeutic agents in the management of PIOD or evaluate a different PIOD cohort with non-COVID aetiology.

Item Type:	Article
Uncontrolled Keywords:	intranasal vitamin a,olfactory dysfunction,post-infectious olfactory dysfunction,covid-19,post-covid smell disorder,mri of cerebral olfactory units,otorhinolaryngology,3* ,/dk/atira/pure/subjectarea/asjc/2700/2733
Faculty \ School:	Faculty of Medicine and Health Sciences > Norwich Medical School Faculty of Social Sciences > School of Psychology
UEA Research Groups:	Faculty of Social Sciences > Research Groups > Developmental Science Faculty of Science > Research Groups > Norwich Epidemiology Centre Faculty of Medicine and Health Sciences > Research Groups > Norwich Epidemiology Centre Faculty of Medicine and Health Sciences > Research Groups > Mental Health Faculty of Medicine and Health Sciences > Research Centres > Mental Health and Social Care (fka Lifespan Health) Faculty of Science > Research Groups > Statistics Faculty of Medicine and Health Sciences > Research Groups > Health Services and Primary Care Faculty of Medicine and Health Sciences > Research Groups > Epidemiology and Public Health Faculty of Medicine and Health Sciences > Research Centres > Public Health Faculty of Medicine and Health Sciences > Research Groups > Norwich Clinical Trials Unit Faculty of Medicine and Health Sciences > Research Groups > Respiratory and Airways Group Faculty of Medicine and Health Sciences > Research Centres > Metabolic Health
Related URLs:	https://academic.oup.com/chemse/advance-...
Depositing User:	LivePure Connector
Date Deposited:	27 Feb 2026 16:30
Last Modified:	27 Feb 2026 16:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/102113
DOI:	10.1093/chemse/bjag001

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