Key messages
We found no evidence to support the use of ivermectin for the treatment of COVID-19 or for preventing SARS-CoV-2 infection. The evidence base has slightly improved in this update, but remains limited.
Assessment of ivermectin is continuing in 31 ongoing trials, and we will update this review again when their results become available.
What is ivermectin?
Ivermectin is a medication used to treat parasites, such as intestinal worms in animals, and scabies in humans. It is an inexpensive medicine and is widely used in regions of the world where parasitic infestations are common. Ivermectin has few unwanted effects.
Medical authorities have not approved ivermectin for COVID-19.
What did we want to discover?
We wanted to update our knowledge about whether ivermectin reduces death, illness, and duration of infection in people with COVID-19, or if it is useful in preventing infection. We included trials comparing the medicine to placebo (a dummy treatment), usual care, or treatments for COVID-19 that are known to work to some extent, such as dexamethasone. We excluded trials comparing ivermectin with other medicines that do not work, such as hydroxychloroquine, or whose effectiveness against COVID-19 is uncertain.
We assessed the effects of ivermectin in infected people on:
- the risk of dying;
- whether people’s COVID-19 got better or worse;
- quality of life;
- serious and non-serious unwanted effects;
- becoming free of the virus.
For prevention, we looked for the effect on preventing SARS-CoV-2 infection and COVID-19 illness.
What did we do?
We searched for randomized controlled trials investigating ivermectin for preventing or treating COVID-19. People treated in hospital or as outpatients had to have laboratory-confirmed COVID-19.
In this update, we also investigated the reliability of the trials and only included them if they met clear ethical and scientific standards.
We compared and summarized the results of the trials and rated our confidence in the evidence, based on common criteria such as trial methods and sizes.
What did we find?
We excluded seven of the 14 trials included in the previous review because these trials did not meet expected ethical and scientific standards. Together with four new trials, we included 11 trials with 3409 participants that investigated ivermectin combined with any usual care compared with the same usual care or placebo.
For treatment, there were five trials with people hospitalized with moderate COVID-19 and six trials with outpatients with moderate COVID-19. The trials used different doses of ivermectin and different durations of treatment.
No trials investigated ivermectin for preventing SARS-CoV-2 infection.
We also found 31 ongoing trials, and 28 additional trials that still require clarification from the authors or are not yet published.
Main results
Treatment for people in hospital with COVID-19
We are uncertain whether ivermectin compared with placebo or usual care at 28 days after treatment:
- leads to more or fewer deaths (3 trials, 230 people);
- worsens or improves patients’ condition, assessed by the need for ventilation or death (2 trials, 118 people);
- increases or reduces serious unwanted events (2 trials, 197 people).
Ivermectin compared with placebo or usual care at 28 days after treatment may make little to no difference to:
- improvement in patients’ condition, assessed by discharge from hospital (1 trial, 73 people);
- non-serious unwanted events (3 trials, 228 participants).
Seven days after treatment, ivermectin may make little to no difference in reducing negative COVID-19 tests (3 trials, 231 participants) compared with placebo or usual care.
Treatment for outpatients with COVID-19:
Ivermectin compared with placebo or usual care at 28 days after treatment probably makes little to no difference to the number of people who die (6 trials, 2860 people).
Ivermectin compared with placebo or usual care at 28 days after treatment makes little to no difference to quality of life (1 trial, 1358 people).
Ivermectin compared with placebo or usual care at 28 days after treatment may make little to no difference to:
- worsening of patients’ condition, assessed by admission to hospital or death (2 trials, 590 people);
- serious unwanted events (5 trials, 1502 people);
- non-serious unwanted events (5 trials, 1502 participants);
- improving people’s COVID-19 symptoms at 14 days after treatment (2 trials, 478 people);
- number of people with negative COVID-19 tests 7 days after treatment (2 trials, 331 people).
What are the limitations of the evidence?
Our confidence in the evidence, especially for outpatients, has improved since the last version of the review because we were able to look at more participants included in higher-quality trials. Although we are moderately confident about our findings on the risk of death and people’s quality of life, confidence in the evidence is still low for many other outpatient and hospital outcomes because only a few events were measured. Methods differed between trials and did not provide information we were interested in, such as relevant outcomes.
How up to date is this review?
The systematic literature search is up to date to 16 December 2021. In addition, we included trials with > 1000 participants up to April 2022.
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