Vagus nerve device for long COVID: tolerated, not proven

Long COVID, or post-acute sequelae of SARS-CoV-2 infection, describes symptoms persisting beyond 90 days after infection and may affect at least 10% of people who catch the virus. Its cause remains unknown; leading theories include persistent viral particles, immune dysfunction and imbalance of the autonomic nervous system, with the vagus nerve implicated in particular. Because the vagus nerve helps regulate inflammation, stimulating it non-invasively has been floated as a plausible therapeutic route. There are currently no approved treatments for the condition and rates of complete recovery are very low, which makes even early-stage testing of candidate interventions worth doing carefully.

Researchers at a post-COVID care clinic ran a pilot randomised controlled trial to test feasibility, safety and exploratory efficacy of a handheld external transcutaneous cervical vagal nerve stimulation device. Participants were randomised either to the stimulation group, using the device for two minutes three times a day, or to a control group receiving no stimulation, over a 12-week study period. The primary endpoint was Post-COVID Functional Status grade, with secondary outcomes covering long COVID-related fatigue and other symptoms. Participants completed validated questionnaires and also underwent PET-CT scans and inflammatory cytokine measurement at baseline and at 12 weeks.

All 18 randomised patients — 8 assigned to stimulation and 10 to control — completed the full 12 weeks, which speaks to feasibility and tolerability. Participants using the device showed observed improvements on the PHQ-9 depression scale, the PROMIS-F fatigue measure and the COMPASS-31 autonomic symptom questionnaire relative to controls, but none of these differences reached statistical significance. Cortisol and DHEA were observed to rise less in the stimulation group than in controls, and again these changes were not statistically significant. The authors' conclusion is limited to the device being well tolerated and possibly promising, rather than effective.

This is an early feasibility study rather than an efficacy trial, and it should be read as establishing that the approach can be delivered and completed rather than that it works. The directional signals across mood, fatigue and autonomic scores are consistent with the vagal-imbalance hypothesis for long COVID, but with this few participants a chance pattern is entirely plausible. The absence of a sham device means expectation effects cannot be separated from any physiological effect. What remains open is whether a properly powered, sham-controlled trial would confirm any of these trends, and whether the PET-CT and cytokine data point to a mechanism.

The honest read is that this tells you the device was safe and usable across 12 weeks, not that it treats long COVID. Directional improvements that miss statistical significance in a group this small are exactly the kind of finding that often disappears in larger trials. For anyone living with long COVID, it is a reason to watch this line of research rather than to draw conclusions from it. The wider context — a chronic condition with no approved treatments — explains why researchers are exploring options like this, but that urgency does not lower the evidence bar.