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, 51. ISSN 0379-864X

Microsoft Word (rba08-Philpott_etal_The_APOLLO_) - Published Version Available under License Creative Commons Attribution. Download (1MB)

Abstract

Postinfectious olfactory dysfunction (PIOD) is common in COVID-19 patients. This 2-arm double-blinded randomized controlled trial (RCT) aimed to establish proof-of-concept for vitamin A versus placebo as a treatment modality for patients with PIOD. This study compared 9,000 IU daily self-administered vitamin A intranasal drops versus peanut oil drops over 12 wk 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 wk. 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 analyzed. There was no significant difference in the change in OBV between both groups. Aside from an improvement in the 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 etiology.

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:	http://www.scopus.com/inward/record.url?... https://academic.oup.com/chemse/advance-...
Depositing User:	LivePure Connector
Date Deposited:	27 Feb 2026 16:30
Last Modified:	13 Mar 2026 08:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/102113
DOI:	10.1093/chemse/bjag001

Downloads

Actions (login required)

View Item