The science on Ivermectin for Covid-19: Preliminary data is not enough, much more evidence is needed

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  • While Covid vaccines have claimed the spotlight, there are other potential treatments that may help prevent or treat Covid-19
  • One of these potential drugs, which is increasingly being promoted, is ivermectin, an antiparasitic 
  • Sufficient evidence is, however, currently lacking, although accelerated efforts to test ivermectin in humans are ongoing

The Covid-19 vaccines have taken centre stage in the race to end the pandemic. However, vaccine rollout will take a long time before it covers the entire global population. In the meantime, scientists are looking to develop other targeted therapies for the disease, caused by SARS-CoV-2.

One drug that has gained particular interest within the last couple of months is ivermectin, a parasiticide that is also used to treat a range of tropical diseases in humans not commonly seen in South Africa, as well as scabies and head lice, according to the South African Health Products Regulatory Authority (SAHPRA).

'Promising results'

The drug is registered for use in animals in South Africa, but is currently not registered for prophylaxis (prevention of disease) or treatment of Covid-19 in humans. 

The New York Times, however, lists ivermectin as one of the 22 most-talked-about treatments for Covid, but since most studies are still at early stages of research, its current status for treating Covid is placed in the category “tentative or mixed evidence”. This label is described by The Times:

“Some treatments show promising results in cells or animals, which need to be confirmed in people. Others have yielded encouraging results in retrospective studies in humans, which look at existing data rather than starting a new trial. 

“Some treatments have produced different results in different experiments, raising the need for larger, more rigorously designed studies to clear up the confusion.”

We take a look at what some of the latest studies and clinical trials (some ongoing) show about the effectiveness of ivermectin in treating or preventing Covid-19.

Meta-analysis

Earlier this month, the SAHPRA referenced a recent meta-analysis (systematic review) of the clinical trial data for the treatment of Covid, which was carried out by Dr Andrew Hill of the University of Liverpool.

The meta-analysis concluded that the use of ivermectin in the management of Covid-19 is associated with faster time to viral clearance and shorter duration of hospitalisation, among other findings.

The report, based on data from over 1 400 patients, is available publicly, and Hill commented on the findings in a video posted on YouTube. However, the study has not yet been published in a peer-reviewed scientific journal.  

As Thomas Scriba, Professor of Infectious Disease Immunology, University of Cape Town, previously explained to Health24, a scientific publication that has gone through peer review allows true scrutiny of the results. 

Hill himself has clarified a number of important limitations of this study, including the results being based on limited randomised trials. He therefore concluded that well-designed clinical trials are required to provide sufficient scientific data for the use of ivermectin for the treatment of Covid-19.

Recent study not peer-reviewed

A recent study conducted at the All India Institute of Medical Sciences, India, has shown that ivermectin can reduce the in-hospital mortality rate of Covid patients.

The clinical trial included a randomised, placebo-controlled study, and 112  patients were included in the final analysis. It is currently available on the medRxiv preprint server.

However, like the study by Hill, it has yet to be evaluated by the medical community.

Understanding importance of peer-reviewed studies 

Preprint server medRxiv also explains the importance of studies being peer-reviewed: 

“Before formal publication in a scholarly journal, scientific and medical articles are traditionally certified by ‘peer review’. In this process, the journal’s editors take advice from various experts–called ‘referees’ – who have assessed the paper and may identify weaknesses in its assumptions, methods, and conclusions. 

“Typically a journal will only publish an article once the editors are satisfied that the authors have addressed referees’ concerns and that the data presented support the conclusions drawn in the paper.”

The preprint server, therefore, only reports new medical research (that has yet to be evaluated) and should not be used to guide clinical practice, it says.

Trial involving migrant workers in Singapore 

The National University Hospital in Singapore ran a trial involving 4 257 volunteers last year to see if ivermectin can prevent people from getting infected with Covid-19. 

The purpose of the study was to look at ivermectin as a preventive treatment for migrant workers at high-risk of Covid-19. Only male volunteers between the ages of 21 and 60 years were involved in this study.

No results have been posted as yet, so as it stands, there is no solid evidence to demonstrate that it works against Covid-19.

Earlier study incorporating cell culture

In April 2020, Australian researchers conducted a cell culture study (not involving humans) testing ivermectin. They noted that since ivermectin is FDA-approved for parasitic infections, it therefore has potential for repurposing.

Their findings, published in the journal Antiviral Research, reported that the drug was able to eliminate SARS-CoV-2 within 48 hours. However, they used a dosage that was so high it might have dangerous side effects in humans. 

Professor Ian Sanne, an infectious diseases specialist and CEO of Right to Care, recently told Health24 that the use of ivermectin as a prophylaxis in unknown doses in humans has a toxicity profile that includes blindness, neurological side effects and liver toxicity.

Science is lacking, top expert stresses

Professor Helen Rees, executive director of the Wits Reproductive Health and HIV Institute at the University of the Witwatersrand discussed the use of ivermectin with eNCA on Sunday and explained why it cannot be used at this stage to treat Covid-19:

“There was initial work done in the laboratory that suggested that ivermectin, which is an old drug… seemed to have activity against SARS-CoV-2. And some studies were done (most of them small; some were what we call ‘observational’)...

“But scientific agencies around the world who have looked at this data are all saying the same thing at the moment, and that is that even though we are wanting to explore old medicines that might have an activity, there is insufficient evidence at the moment that ivermectin works [for preventing or treating Covid-19].”  

While certain studies have highlighted the potential significance of ivermectin in Covid-19 and scientists express glimmers of hope, it requires additional testing in larger randomised controlled trials (RCTs) and dose-response studies to determine whether it is safe and effective to prevent or treat Covid-19.

Statement from MAC

In a statement addressed to Health Minister Zweli Mkhize on 7 January, the Ministerial Advisory Committee (MAC) on Covid-19 also emphasised that while the use of this repurposed medicine is being heavily promoted via social media, "given the limited evidence of efficacy and safety, as well as appropriate dosing of ivermectin, its place in therapy and prophylaxis remains uncertain at this point." 

The statement goes on to say: "There is some in vitro evidence that ivermectin has antiviral activity against SARS-CoV-2... [but] more data is required from adequately powered, well-designed randomised clinical trials to demonstrate the efficacy and safety of ivermectin in both treatment and prevention of Covid-19. Some larger trials are ongoing, and it is hoped that the results will become available within the first quarter of 2021."

Moreover, the statement points to reports of apparent toxicity from overdoses of the drug, and explain that although it is portrayed as safe, it is associated with a range of adverse effects when used in its registered indications in humans.

"Until more robust evidence is available, the routine use of ivermectin for either the prevention or treatment of Covid-19 is not justified. Nonetheless, emerging evidence must be actively sought and carefully reviewed... As always, reports in peer-reviewed publications will be preferred," it states.

READ | Ivermectin not a treatment for Covid-19, warns SA expert

READ | Does baby shampoo help to treat Covid-19? No science backs this up, experts say

READ | OPINION | Why I choose Covid-19 vaccination based on verifiable evidenc

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