The APOLLO Trial: A Proof-of-Concept Study for Vitamin A Nasal Drops in COVID-19 Related Post-Infectious Olfactory Dysfunction
et al., Chemical Senses, doi:10.1093/chemse/bjag001, APOLLO, ISRCTN13142505, Jan 2026
Vitamin A for COVID-19
49th treatment shown to reduce risk in
May 2023, now with p = 0.004 from 14 studies.
No treatment is 100% effective. Protocols
combine treatments.
6,300+ studies for
210+ treatments. c19early.org
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RCT 57 COVID-19 patients with post-infectious olfactory dysfunction showing no significant difference with intranasal vitamin A versus placebo drops. Authors hypothesize that COVID-19's mechanism of damaging sustentacular cells rather than olfactory receptor neurons directly may explain why vitamin A, which promotes olfactory neuron regeneration, did not show a significant effect here.
Standard of Care (SOC) for COVID-19 in the study country,
the United Kingdom, is very poor with very low average efficacy for approved treatments1.
The United Kingdom focused on expensive high-profit treatments, approving only one low-cost early treatment, which required a prescription and had limited adoption. The high-cost prescription treatment strategy reduces the probability of early treatment due to access and cost barriers, and eliminates complementary and synergistic benefits seen with many low-cost treatments.
|
risk of no recovery, 50.4% higher, RR 1.50, p = 0.54, treatment mean 2.58 (±7.19) n=30, control mean 3.88 (±5.17) n=15, ΔTDI.
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| Effect extraction follows pre-specified rules prioritizing more serious outcomes. Submit updates |
Yeap et al., 20 Jan 2026, Double Blind Randomized Controlled Trial, placebo-controlled, United Kingdom, peer-reviewed, mean age 47.2, 12 authors, study period July 2022 - October 2022, post-COVID olfactory dysfunction, trial ISRCTN13142505 (APOLLO).
The APOLLO Trial: A Proof-of-Concept Study for Vitamin A Nasal Drops in COVID-19 Related Post-Infectious Olfactory Dysfunction
doi:10.1093/chemse/bjag001/8430749
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
Protocol The published protocol can be found online at: https://rdcu.be/elYva (Kumaresan et al. 2023) .
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"abstract": "<jats:title>Abstract</jats:title>\n <jats:p>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.</jats:p>\n <jats:p>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.</jats:p>\n <jats:p>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.</jats:p>\n <jats:p>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.</jats:p>",
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Late treatment
is less effective
is less effective
