What randomized trials are ongoing or completed that test specific ivermectin prophylaxis regimens for COVID-19?
Executive summary
Randomized trials specifically testing ivermectin as prophylaxis for SARS‑CoV‑2 infection are sparse, disputed, and — according to major systematic reviews — did not provide clear evidence of prevention as of late 2021, even while dozens of prophylaxis and treatment trials remained ongoing or unreported; authoritative reviewers therefore urged that ivermectin only be used in randomized trials for COVID-19 [1] [2] [3]. Recent registries show at least one new multicenter randomized placebo‑controlled prophylaxis trial registered in 2024, but the corpus of completed, high‑quality RCT evidence for prophylaxis remains limited and contested [4] [2].
1. What the major reviews concluded about prophylaxis trials
Cochrane’s comprehensive reviews up through late 2021 concluded that no trial had reliably demonstrated ivermectin’s ability to prevent SARS‑CoV‑2 infection and reported numerous ongoing trials that might change the picture; their update stated “No trial investigated ivermectin to prevent SARS‑CoV‑2 infection” while also identifying 31 ongoing trials and another set of trials needing clarification — an apparent tension that reflects trials reported as planned or cluster‑based but without completed, high‑quality prophylaxis endpoints available for meta‑analysis at that time [2] [5].
2. Completed randomized prophylaxis studies: noisy signals, weak designs
A handful of small or cluster randomized efforts claimed prophylaxis signals — for example, the Ivercar‑Tuc program (ivermectin plus iota‑carrageenan) and the Chahla cluster trial among healthcare workers — which were captured as preprints or registry entries and included in some systematic reviews, but these studies varied in design, blinding and endpoints and were often reported outside peer‑reviewed literature, reducing their weight in high‑quality syntheses [1] [6] [7].
3. Ongoing randomized trials: numbers, heterogeneity, and new registrations
Multiple independent sources counted dozens of active clinical trials testing ivermectin for prevention or treatment: Cochrane and allied reviews reported roughly 31 ongoing RCTs as of late‑2021 (with additional studies awaiting classification), while regional advisory groups and registry tallies put the number of registered COVID‑19 ivermectin trials higher — for example, Alberta’s summary noted 38 ongoing clinical trials on clinicaltrials.gov including 31 RCTs — and registries continued to accept new trials into 2024, including a registered multicenter randomized double‑blind placebo‑controlled prophylaxis study (NCT05305560) [5] [8] [4].
4. Quality problems, contested positives, and why conclusions diverge
The literature is fractured: several meta‑analyses and advocacy reviews asserted strong prophylactic or therapeutic benefits, often relying on smaller trials and non‑peer‑reviewed reports, while methodologists flagged bias, inconsistent registrations, and even forged or non‑feasible data in some high‑profile studies (for example the widely criticized Elgazzar paper), which undermines pooled estimates and explains divergent conclusions between proponents and independent reviewers [9] [10]. Major public health bodies (EMA, NIH, WHO) advised against routine use outside trials, emphasizing that randomized evidence to date was insufficient or negative for meaningful clinical benefit in treatment and lacked reliable prevention data [11] [12].
5. Bottom line: specific prophylaxis regimens tested and the evidence gap
Published randomized work that explicitly tested ivermectin as pre‑exposure or post‑exposure prophylaxis is limited to small, often cluster or combination‑therapy trials (e.g., ivermectin with iota‑carrageenan) and pilot trials with heterogeneous dosing (examples include single‑site clusters and pilot RCTs reported as preprints), none of which produced a definitive, high‑certainty signal accepted by major systematic reviewers as proof of prophylactic efficacy; meanwhile, many registered randomized prophylaxis trials remain ongoing or unpublished, and at least one large multicenter randomized prophylaxis trial was registered in 2024 [1] [6] [4] [2].