Efficacy of Ivermectin Against Covid-19

All 63 studies central estimates

Note added 10/11/21: The microchemistry evidence in favour of Ivermectin now looks definitive. In particular it looks like Ivermectin is at least as effective, and probably more effective, than the new Pfizer anti-viral. The main difference is that Ivermectin is virtually free, whereas Pfizer will be charging the earth for their new drug. Watch this video: https://www.youtube.com/watch?v=ufy2AweXRkc


Apologies for this off-topic post, but I’ll make it brief.

I have carried out an independent literature review of the efficacy of Ivermectin in prophylaxis or treatment of Covid-19. I thought, having done it, I might as well make it more widely available. It is here.

The conclusion is that the balance of evidence is in favour of efficacy, and that Ivermectin is a safe drug. Claims that abound from Google searches that excessive doses are required for clinical efficacy are simply false.

As of their last report (March 2021), the World Health Organisation continues to recommend NOT using Ivermectin against Covid-19, except in the context of clinical trials. The conclusions from their own meta-analysis are strangely at odds with what I found in the literature.

I found many papers calling for large scale trials, going back to early in the pandemic. But the funding necessary for large trials, which would have to come from national or international authorities, or from Big Pharma, did not materialise and so neither did the large scale trials. Instead we have many small trials, funded locally by individual research centres or hospitals. In this situation, when conducting meta-analyses, it becomes necessary to include studies which might normally be rejected – otherwise the situation becomes a self-fulfilling impasse in which lack of big funding means lack of big trials means “no statistically significant evidence”. But the statistical significance arises only when many small trials are aggregated.

11 thoughts on “Efficacy of Ivermectin Against Covid-19

  1. M Winter

    The Carvallo studiy from Argentina, like the Egyptian Elgazzar study, is now accused of being fraud. I’ve looked at the specific accusation, and it looks pretty damning, no one can point to corroborating evidence that the study took place at all.

    That highlights the problem of meta studies in general. They’re assuming everyone acts in good faith, that errors are honest mistakes. Even then, adding up the results is non-trivial (I notice a lot of studies are about Ivermectin-and-something-else, making the causal effect hard to disentangle).

    When something becomes a culture war issue, there are some people who simply don’t, as I bet you’ve noticed on the main topic of this blog. On the one hand you have people who just convince themselves their side is right because it’s their side. But you also have pure grifters. It’s probably possible to make money by pushing Ivermectin, by e.g. speculating in the stock price of producers of it or its precursor chemicals.

    1. William Collins Post author

      Thanks, re Carvallo – that’s worth knowing. Unfortunately, scientific papers dependent on studies are wide open to fraud. I suppose the question is – why did it become a culture war issue? I noted that most papers ended in a plea for large scale trials, which has not happened.

  2. Philip G Griffiths

    The only problem here is that meta-analysis of trials is not just an exercise in ‘vote-counting.’ This is because there are usually many more smaller studies at high risk of bias (in the statistical sense) than larger studies at low risk of bias. The Cochrane collaboration ( a non-profit-making body) usually rates studies for risk of bias. For example, random sequence generation, allocation concealment, similarity of groups at baseline, blinding of participants and researchers, attrition bias, and reporting bias. Studies at a high risk of bias are usually excluded or at least given limited weight. This is with good reason, positive effects found by pooling multiple small studies at high risk of bias are seldom replicated by large-scale trials.

    1. Ron

      The use of poor quality data sets when there are no large well powered trials is not uncommon in medical science and health technology assessment. Many of the drugs approved by the FDA have poorer data sets than those available for Ivermectin. Meta-analyses based of relatively poor quality studies should not be preferred to those including good quality studies, but should not be dismissed in the abscence of better quality evidence. Very few of the drugs we use today for rare or orphan diseases would be approved by the FDA following your view.

      1. Philip Griffiths

        Can you name a drug approved by the FDA with a data set poorer than ivermectin?
        There have been too many medical reversals where drugs and surgical treatments that were thought to be beneficial on the basis of pooled poor studies proved to be useless or even harmful.

    1. William Collins Post author

      Big Pharma usually fund large clinical trials on the expectation of commercial profit. The obvious explanation is that Big Pharma was disinclined to fund studies that could net them no cash. I believe this is the case as Ivermectin is certainly cheap. No doubt there are patent issues behind this, but the patent position is too complex for me to understand. I know the FDA recently licensed a company to manufacture Ivermectin for human use. So I presume the original patent holder (Merck) is out of the picture.


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