Wednesday 18 August 2021

Ivermectin: New Bayesian meta-analysis provides further support for its effectiveness in treating Covid-19


This is an updated version of an article that was first published in July 2021

A recent peer reviewed meta-analysis evaluating ivermectin (Bryant et al) concluded that this cheap antiparasitic drug is an effective treatment for reducing Covid-19 deaths. These conclusions were in stark contrast to those of a later study (Roman et al). Although (Roman et al) applied the same classical statistical approach to meta-analysis, and produced similar results based on a subset of the same randomized controlled trials data used by (Bryant et al), they claimed there was insufficient quality of evidence to support the conclusion Ivermectin was effective. But their conclusion is based on a subjective (and possibly biased) assessment ot the 'quality' of the trials; moreover, they wrongly concluded 'no effect' from what was merely weaker evidence of a positive effect.  

Those who are unfamiliar with the way statistics are used to analyse effectiveness in such studies would be very confused by the contradictory conclusions if they looked at the quantified results presented. These are summarised by what is called the risk ratio (RR). The RR is an estimate of the death rate of patients taking ivermectin divided by the death rate of patients not taking ivermectin. For example, if we knew for sure that 2% of patients taking ivermectin died compared to 4% not taking ivermectin then the RR would be 0.5.  If the RR is clearly less than one then it is reasonable to conclude the treatment is effective.

Bryant and Roman provide very similar estimates for the RR: Bryant reports 0.38, while Roman reports 0.37, which seems to mean both agree that ivermectin is effective. However, because the statistics can only provide uncertain estimates of the true death rates, the RR is also presented with upper and lower “confidence interval” bounds – typically 95%.

The Roman study uses fewer data and (as is common in such situations) arrives at wider confidence bounds: 0.12 to 1.13 compared to bounds of 0.19 to 0.73 in Bryant.

Most people assume this means there is a 95% chance the RR lies between the reported upper and lower bounds. But it does not. It relies on a complex notion of what would be observed in multiple theoretical repeated trials.

In classical statistical hypothesis testing, if the upper 95% confidence interval bound is greater than 1, the hypothesis that the RR is greater than 1 “cannot be rejected with sufficient confidence”. 

A new analysis applies an alternative to the classical approach - namely a Bayesian approach - to a subset of the same trial data used in the studies (a summary version of this analysis is to appear in the September issue of American Journal of Therapeutics). It tests several causal hypotheses linking Covid-19 severity and ivermectin to mortality. Applying diverse alternative analysis methods which reach the same conclusions should increase overall confidence in the result. 

The paper show that there is strong evidence to support a causal link between ivermectin, Covid-19 severity and mortality, and: 

i) for severe Covid-19 there is a 90.7% probability the risk ratio favours ivermectin; 

ii) for mild/moderate Covid-19 there is an 84.1% probability the risk ratio favours ivermectin. 

Also, from the Bayesian meta-analysis for patients with severe Covid-19, the mean probability of death without ivermectin treatment is 22.9%, whilst with the application of ivermectin treatment it is 11.7%. 

Since the first version of the Bayesian analysis was reported in early July, some concerns have been raised about the veracity of some of the studies, notably that of Elgazzar. While some have noted that these concerns may be based on Western elitism (the studies criticized all come from Africa and Asia), the revised version of the paper nevertheless addresses the concerns. Specifically, it evaluates the sensitivity of the conclusions to any single study by removing one study at a time. In the worst case, where Elgazzar  is removed, the results remain robust, for both severe and mild to moderate Covid-19. 

The paper also highlights advantages of using Bayesian methods over classical statistical methods for meta-analysis. But it should be noted that all studies included in the analysis were prior to data on the delta variant.

18 August UPDATED paper: Martin Neil and Norman Fenton (2021) "Bayesian Hypothesis testing and hierarchical modelling of Ivermectin Effectiveness in Treating Covid-19 Disease

(NOTE: there is an error in the Appendix page 11. The  Binomial formula combinatorial term has pi when it should be xi)

Original paper: Martin Neil and Norman Fenton (2021) "Bayesian Meta Analysis of Ivermectin Effectiveness in Treating Covid-19 Disease"  


Postscript: As with previous papers that 'challenge' the main stream Covid-19 narrative, the paper was not accepted on medRxiv. The explanation (see below) is curious given that the whole point of a preprint server is to publish unreviewed work (and they normally automatically accept anything within scope):



  1. My family has used Ivermectin, succely as previous treatment against Covid-19.

  2. Roman paper on meta-analysis : Is this the paper with A.V.Hernandez as a coauthor ?
    This paper has a very troubling history

  3. They will not post as preprint as they just do not want the heat. Understandable and shows how much pressure is being applied by govt sources and perhaps pharma to constrain ivm.

  4. Ivermectin is a drug that uses negative effects on the body and also eliminates the virus. There is a demand to stay aware of the side effects like diarrhea as well as throwing up. You ought to discover the views of the wellness organizations connected to the infection getting rid of in the physical body. It is the most ideal selection for eliminating the virus and deterrence from covid-19. If you see this website, you are going to get a growing number of information about Buy Ivermectin Online.

  5. Great blog. Modafinil 200mg is used to treat narcolepsy Such as a period of stopped breathing during sleep. Buy Modafinil Online to reduces extreme sleepiness.

  6. Thanks for sharing the wonderful post with us!It is given by mouth or by injection.Ivermectin 3mg price in usa, Ivermectin 3mg tablets for sale,Ivermectin 3mg dosage, Ivermectin 3mg online,As an analeptic, modafinil 200mg can treat narcolepsy, obstructive sleep apnea and shift work disorder.
    ivermectin 12mg side effects
    fluoxetine 40mg dosage
    Hydrochloroquine 200 mg side effects
    Modafinil 200mg tablets price

  7. Great post, really helpful. Want to know How Long Does Modafinil Last and how it works?.

  8. Kamagra Polo(Sildenafil 100mg) is used to get and sustain an erection in Erectile Dysfunction in men.
    You can also e-mail us at: sales@Rsmenterprises.In
    Or Chat on WhatsApp with +91 92163-25377

    Buy Sildenafil 100mg
    Buy Kamagra Polo

  9. Thanks for sharing this blog with us. Buy Celebrex Online to treat as a pain relevier.

  10. This comment has been removed by the author.

  11. Buy Ivermectin drug made use of for dealing with viral disease. Ivermectin for people is utilized to take care of Covid-19. Buy Ivermectin 12 is used for viral consideration treatment for individuals. Hydroxychloroquine 200 Mg is an opponent of viral medication remedies for Covid-19 Patients. Ziverdo Kit is the most effective solution for viral factor to consider as well as Covid-19 Treatment. For more information regarding to Buy Ivermectin click on this link