Up to date, there are sixteen ivermectin studies on covid as prophylaxis. All of them validate the effectiveness in preventing a symptomatic disease.[i] The studies also underline a positive dose-response relationship. The results range from near 100% effectiveness in weekly doses to 50% in the 42-day period following a single dose. As onchocerciasis program comprises one dose every half-year, it is reasonable to think that the protection doesn’t last that long. A deeper look could give us a better understanding.
In March 2021, Japanese researchers published a study about African countries and Ivermectin on Covid-19. [ii] In the study, the authors evaluate COVID-19 outcomes in African regions. They split the countries into two groups: A group of countries with ivermectin programs to fight onchocerciasis, and another group with the remaining countries. As an aggregate, countries with the program have had a small fraction of Covid cases and deaths than the aggregation of countries without interventions. After ruling out the age disparities, the authors concluded: “treatment with ivermectin is the most reasonable explanation”.
Undoubtedly, age is a vital factor in COVID-19 outcomes, but it is not the only one. There are other aspects to consider and cancel out before concluding in favor of ivermectin. We know more testing means more cases. Were there fewer tests in the “ivermectin group”? We know that winter affects the outbreaks, are winter in the “ivermectin group” milder? Should we analyze international travelers? Should we examine the medical system or cultural traditions?
Testing strategy drive case and death count
Covid testing has been the known method of counting cases and deaths but is not reasonable to compare countries when testing strategies differ. Regions with extensive testing and modest incidence can detect much more cases than a modest testing with mounting incidence. The analysis of the number of tests and the positivity presents a much accurate view. Positivity could be a reliable indicator of the virus prevalence at a moment in time. Looking at the data, the vast disparity in testing can explain the considerably larger case and death count in “non-ivermectin countries” like South Africa, Tunisia, or Morocco. It is even more telling within the groups, countries in with a similar level of testing show similar levels of cases. That means that a difference in testing is a substantial driver of the lower-case incidence in the “ivermectin group.” As an illustration, Morocco has eight times more cases than Uganda, but six times more tests. South Africa that has twenty times more cases than Nigeria, but eighteen times more testing.
It is a common practice that in regions with limited tests, people with symptoms are the priority. Therefore, positivity reveals an acceptable covid share among those with flu-like symptoms. In regions with low testing like Africa, positivity rate might operate as a predictor of cases in the same way sera-prevalence samples predict population level antibodies. On average, the positivity in the “non-ivermectin group” has been 50% higher than the “ivermectin group” (10% vs 7%.) This difference supports the idea of better outcomes in the “ivermectin group” even after excluding the impact of the difference in the number of tests. There are certainly more factors, and they could be one.
Other factors
Traditional Chinese Medicine and Ayurveda are well-known Asian medical systems. Likewise, Sub-Saharan had maintained ancient medical traditions or “bush medicine.” Their knowledge comprises the use of natural medicine and techniques developed through thousands of years of treating various diseases.
A suitable example is the wisdom shared by the African slave Onesimus in 1721. He taught how to prevent smallpox in Boston USA, and his knowledge led to vaccine development. [iii] This same ancient science holds dengue epidemics under control in Africa. Natural medicine is in wide use in Sub-Saharan Africa where doctors per capita is at least 4 times less than South Africa’s or that countries in Northern Africa. Ancient natural medicine it is another determinant factor in pandemic management.
The weather and the tourism played their role too. In Africa, Winter only affects Northern and Southern countries.[iv] All “ivermectin countries” are in Central Africa where temperature averages are above 70 F (20 C). The lack of winter also influenced a lower incidence in Central Africa. As international travelers drove covid, tourism is an important factor. Unsurprisingly, the number of arrivals in “ivermectin countries” is about 10 times fewer that the one in Northern Africa or in South Africa.[v] Then, international arrivals also influenced the lower Covid incidence in Central Africa.
Conclusion
Ivermectin interventions to treat parasites might have influenced COVID-19 outcomes in Central Africa, but they aren’t the leading driver. Other various factors better explain the difference in the aggregate results. The primary explanation is testing. The correlation between tests and cases or deaths is very strong. Other factors, like the use of natural medicine, the lack of winter, and the number of international arrivals, also played a fundamental role.