Incorrect: The claim that ivermectin works as a vaccine and prevents future infections (prophylaxis) by SARS-CoV-2, the virus that causes COVID-19, is based on a misunderstanding of the mode of action of vaccines. Vaccines stimulate the formation of long-lasting immunological memory that protect vaccinated individuals from subsequent infections. By contrast, a patient must constantly take a prophylactic drug to maintain its preventative effect.
FULL CLAIM: Ivermectin “is a safe and widely available treatment for coronavirus”; it works “like a vaccine”; refusing it “no different than murdering the patients who need them”
The COVID-19 pandemic that has swept the world since early 2020 sparked an intense research effort to uncover cures for it. To date, scientific and general public media outlets presented several molecules as possible cures for COVID-19, such as hydroxychloroquine or remdesivir.
Since April, a drug named ivermectin, which is used to treat parasitic infections, triggered public interest due to claims on social media that the drug can cure COVID-19 and save lives. One example of this claim can be seen in this video by One America News Network. Some media touted it as a “wonder drug”, which led several countries to include it in their official treatment recommendations for COVID-19. However, scientific evidence supporting ivermectin’s use as a COVID-19 treatment is scant and appropriate clinical trials are still lacking, as this review explains below.
Claim 1 (Unsupported): Ivermectin “is a safe and widely available treatment for coronavirus”
The claim that ivermectin is a proven cure for COVID-19 started getting viral in the second half of 2020, leading some countries to recommend it as a COVID-19 treatment. Some studies report an antiviral effect of ivermectin on SARS-CoV-2, the virus that causes COVID-19, in the lab. However, the available clinical evidence is not strong enough to support the claim that ivermectin is a treatment for COVID-19. Few clinical trials on ivermectin’s efficacy against COVID-19 have reached completion as of January 2021. Most of the available data come from observational studies that do not have the same level of reliability as clinical trials; furthermore, their conclusions are mixed.
Ivermectin is a molecule that is generally used to treat parasitic infections. It was discovered in the 1970s, winning its inventor a Nobel Prize in 2015. Several studies found that ivermectin has an antiviral effect against a large range of viruses, including SARS-CoV-2[1,2]. However, these data are purely in vitro, meaning that the experiments were conducted on cells growing in the laboratory and not in living animals or humans.
Following the discovery of its in vitro antiviral activity against SARS-CoV-2, many laboratories assessed whether this molecule could be used to treat COVID-19 in humans. David Jans and Kylie Wagstaff, the author of an April 2020 research paper that first described the in vitro antiviral activity of ivermectin against SARS-CoV-2, counted 68 current clinical trials and surveys on the effect of ivermectin on COVID-19 in humans.
However, available information from clinical studies databases, such as ClinicalTrials run by the U.S. National Library of Medicine, indicates that only seven of those 68 reached completion and released their results. Of them, only two are randomized, controlled, blinded clinical trials, which are considered the gold standard for testing drug safety and efficacy[4,5]. In these trials, patients are randomly assigned to either a group receiving the treatment (in this case, it would be a drug regimen including ivermectin) and a control group that receives a placebo. By randomizing the group assignments, characteristics of the patients, such as age, sex, lifestyle, genetics, etc., are evenly distributed between the test group and the control group. Blinded trials, as opposed to open label trials, means that patients and health practitioners are unaware of whether they belong to the test group or the control group to avoid any placebo effect. Finally, clinical trials that are conducted on large populations minimize the impact of chance influencing the study outcomes.
By contrast, in observational studies, researchers either follow the progression of a disease in patients without intervening in their drug regimen or assess the outcomes of former patients based on knowledge about the treatment they received. Observational studies are easier to set up and usually less expensive than clinical trials, which makes them a useful tool, but they are also more prone to bias. As a result, they are regarded as a lower standard of evidence than clinical trials[6,7]. As of January 2020, the majority of available clinical results about ivermectin and COVID-19 come from observational studies. Therefore, the evidence available so far is informative, but not strong enough to support ivermectin as a cure for COVID-19.
Some studies report that ivermectin has a positive effect on patients with COVID-19, but the study designs are so variable that it is not possible to assess how useful ivermectin might be for treating COVID-19. It is also unclear what dose of ivermectin should be administered and which patient groups it should be used for. For instance, a randomized, controlled, blinded clinical trial on 72 hospitalized patients found that ivermectin alone, but not ivermectin given together with doxycycline, could speed up the viral clearance from COVID-19 patients’ bodies, albeit without changing the duration of their symptoms. However, the authors note that “the study sample was too small (n = 72) to draw any solid conclusions”.
A retrospective observational study looked at the course of COVID-19 patients that received ivermectin and found they had lower mortality among heavily sick patients compared to those that didn’t receive ivermectin. But the small size of the study and its observational nature (as opposed to randomized clinical trials) led the authors to warn, “Appropriate dosing for this indication is not known, nor are the effects of ivermectin on viral load or in patients with milder disease. Further studies in appropriately designed randomized trials are recommended before any conclusions can be made.”
By contrast, other laboratories reported no effects of ivermectin on COVID-19 in patients. An observational study on patients suffering from severe COVID-19 symptoms showed no effect of ivermectin on their clinical or epidemiological outcomes.
Based on these results, Andrew McLachlan, Dean of Pharmacy at the University of Sydney commented: “Many of the current studies have low numbers of participants, weak study designs, and inconsistent (and relatively low) ivermectin dosing regimes, with ivermectin frequently given in combination with other drugs.”
In summary, some clinical data suggests that ivermectin might be beneficial for at least some types of COVID-19 patients. However, the clinical data available so far is not strong enough to claim that ivermectin is a “treatment” for COVID-19. Several scientific papers reviewing available evidence thus concluded:
““The clinical efficacy and utility of ivermectin in SARS CoV-2 infected patients are unpredictable at this stage […] we await results of well-designed large scale randomized controlled clinical trials exploring treatment efficacy of ivermectin to treat SARS-CoV-2”
“it is clear that only the results from large rigorous randomized clinical trials will definitively establish ivermectin’s utility to treat or prevent SARS-CoV-2 infection.” ”
Claim 2 (Unsupported): “refusal to make these medicines available is no different than murdering the patients who need them”.
The claim that the lack of support for ivermectin’s use at the administrative and political level amounts to murder implies that ivermectin effectively prevents COVID-19 related deaths. However, the clinical evidence indicating that ivermectin could reduce mortality in COVID-19 patients is weak.
One observational study of 250 patients found that ivermectin would reduce the mortality among hospitalized COVID-19 patients from 6.8% to 0.9%. Another retrospective study on 280 patients also found a lower mortality among the patients group treated with ivermectin (13%, as opposed to 24% in the control group). The majority of available studies to date did not assess the impact of ivermectin on mortality from COVID-19.
Although these studies may appear encouraging at first, their design as observational studies rather than clinical trials limits the significance of their results. Dominique Costagliola, an epidemiologist and biostatistician at the Pierre Louis Institute of Epidemiology and Public Health in France warned that these studies contain limitations. For instance, it is difficult to ensure that the beginning of the observation period was the same for all patients in the study. For that reason, the authors of the study with 280 patients concluded, “Further studies in appropriately designed randomized trials are recommended before any conclusions can be made”. In short, the available evidence is still limited and not sufficient to fully support the claim that ivermectin prevents COVID-19 deaths.
Claim 3 (Incorrect): “It would work like a vaccine”
The video from One America News Network also relayed a statement by Thomas Borody, a gastroenterologist at the Center for Digestive Diseases in Australia and a proponent of the efficacy of ivermectin. Borody claimed that ivermectin can work “like a vaccine” because it would protect people from developing a SARS-CoV-2 infection.
This claim is incorrect. Even if ivermectin could prevent SARS-CoV-2 infections in people, this effect would only last while people take the drug. By contrast, vaccines offer long-lasting protection against infections. Indeed, vaccines work by helping a person’s immune system recognize and build defenses against the pathogen without the risks associated with natural infection. This confers the vaccinated person with protection against a future infection with the actual pathogen without the need for continuous medication. It is still unclear how long vaccine-induced immunity will last in the case of COVID-19 as it is a novel virus. But current data indicates that it may last for at least eight to nine months.
In summary, the claim that ivermectin is a proven cure for COVID-19 is unsupported at this point in time. Some observational studies suggest that ivermectin can help reduce the amount of virus and improve COVID-19 symptoms or mortality in infected people. However, the level of confidence in these studies is low. Large, multi-centric, randomized, controlled, blinded clinical trials are still needed to demonstrate the efficacy of ivermectin against COVID-19. At the moment, there is no strong data to support the claim that ivermectin will significantly save more lives or protect people in the same way as a vaccine.
Associated Press also fact-checked similar claims about ivermectin and found them to be unsupported.
- 1 – Heidary & Gharebaghi (2020) Ivermectin: a systematic review from antiviral effects to COVID-19 complementary regimen. The Journal of Antibiotics.
- 2 – Caly et al. (2020) The FDA-approved drug ivermectin inhibits the replication of SARS-CoV-2 in vitro. Antiviral Research.
- 3 – Jans & Wagstaff (2020) The broad spectrum host-directed agent ivermectin as an antiviral for SARS-CoV-2? Biochemical and Biophysical Research Communications.
- 4 – Akobeng (2005) Understanding randomised controlled trials. Archives of disease in childhood.
- 5 – Sibbald & Roland (1998) Understanding controlled trials: Why are randomised controlled trials important? British Medical Journal.
- 6 – Gueyffier & Cucherat (2019) The limitations of observation studies for decision making regarding drugs efficacy and safety. Therapies.
- 7 – Wang et al. (2015) Reporting of Limitations of Observational Research. JAMA Internal Medicine.
- 8 – Ahmed et al. (2020) A five-day course of ivermectin for the treatment of COVID-19 may reduce the duration of illness. International Journal of Infectious Diseases.
- 9 – Rajter et al. (2020) Use of Ivermectin Is Associated With Lower Mortality in Hospitalized Patients With Coronavirus Disease 2019. Chest.
- 10 – Camprubi et al. Lack of efficacy of standard doses of ivermectin in severe COVID-19 patients. PloS One.
- 11 – Pandey et al. (2020) Ivermectin in COVID-19: What do we know? Diabetology and Metabolic Syndrom.
- 12 – Khan et al. (2020) Ivermectin Treatment May Improve the Prognosis of Patients With COVID-19. Archivos de Bronconeumología.