Trial reportChemical senses2026
The APOLLO trial: a proof-of-concept study for vitamin A nasal drops in COVID-19-related postinfectious olfactory dysfunction.
Trial report in Chemical senses, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
2 citing papers in PubMed.
- The Norfolk Smell and Taste Clinic Experience-A Decade of Olfactory and Gustatory Dysfunction.Clinical otolaryngology : official journal of ENT-UK ; official journal of Netherlands Society for Oto-Rhino-Laryngology & Cervico-Facial Surgery · 2026Article
- Article
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
12 authors.
Funding
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.
Indexed as
Identifiers
What Socratic holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the Socratic graph.