NOTE: Previous installment (#1) is here. And installment #3 is here.
In this installment of the Minimum Acceptable Efficacy series, we’ll look at Ivermectin, one of the safest medicines (it is approximately 10 times safer than acetaminophen, using raw number of reports in WHO’s VigiAccess database). As before, 50% efficacy is required to meet a standard of efficacy against COVID.
That is the required magnitude of effect, but there is also a second requirement on the precision of the estimate of the magnitude of effect: the 95% lower limit of the estimated efficacy must be at least 30% efficacy. This report will be confined to a few moderately-large, peer-reviewed, prospective studies on Ivermectin.
Here’s a Feb. 2021 study from Egypt:
At top-right you see close contacts (of index cases of COVID) who either took Ivermectin or not. There were 203 family contacts of COVID cases who took Ivermectin, but only 15 of them presented with symptoms within 14 days of follow-up. In contrast, of those family contacts who did not take Ivermectin, 58% got symptoms.
Here is a breakdown of the numbers, along with an Odds Ratio (OR), and then a Risk Ratio (RR) which reveals the efficacy — the efficacy is computed as: (1 - RR):
In cells C81 and C83, you find the risk ratio (RR) and the 95% limit. The point estimated efficacy of Ivermectin against COVID was found to be 87%, with a 95% lower bound efficacy of 77%. But let’s look for other moderately-large, peer-reviewed, prospective studies that independently confirm Ivermectin’s estimated efficacy against COVID.
Here’s an Aug 2021 study from India:
A double-dose of Ivermectin was given to healthcare workers and then they were followed for a month after that, so as to record any infections. Here is a data table so that you can see the breakdown of the 1147 who got no Ivermectin vs. the 2199 who got two-dose Ivermectin. Numbers in the next column to the right are infections:
With those who got no Ivermectin serving as the reference group, the two cells at very bottom-right show the adjusted relative risk of 0.17 for two-dose Ivermection (83% efficacy). And the 95% lower bound of Ivermectin efficacy against COVID was … yep … you guessed it … 77%. That is a number that we have seen before!
It was the lower bound of Ivermectin’s efficacy against COVID from our first example.
But even though the lower bound of 77% efficacy against COVID already got confirmed by independent researchers, let’s add one more large, peer-reviewed, prospective study from Jan 2022 that used propensity score matching to prospectively evaluate the effect of a large proportion of a city in Brazil all going on Ivermectin:
As you can see in the third row from the bottom, of the 114,000 persons followed who had been taking Ivermectin — compared to 46,000 persons followed who did not — the relative risk of hospitalization was 0.27 (73% efficacy), with a 95% limit of 0.33 (67% efficacy against COVID hospitalization).
The mortality benefit is in the bottom row, with a point estimate of 59% efficacy (59% reduction in the mortality rate from taking Ivermectin), and a 95% lower limit of efficacy against mortality of 45%. That’s promising, and augments earlier findings about how vitamin D meets both of the WHO standards for efficacy against COVID.
With multiple substances meeting WHO standards for efficacy, you would think that officials would be mentioning them more. Stay tuned for further installments.
Reference
[Ivermectin cuts hospitalization by at least 67%] — Kerr L, Cadegiani F A, Baldi F, et al. (January 15, 2022) Ivermectin Prophylaxis Used for COVID-19: A Citywide, Prospective, Observational Study of 223,128 Subjects Using Propensity Score Matching. Cureus 14(1): e21272. doi: 10.7759/cureus.21272. https://www.cureus.com/articles/82162-ivermectin-prophylaxis-used-for-covid-19-a-citywide-prospective-observational-study-of-223128-subjects-using-propensity-score-matching#!/
[Ivermectin cuts infections by at least 77%] — Behera P, Patro B K, Padhy B M, et al. (August 05, 2021) Prophylactic Role of Ivermectin in Severe Acute Respiratory Syndrome Coronavirus 2 Infection Among Healthcare Workers. Cureus 13(8): e16897. doi:10.7759/cureus.16897. https://www.cureus.com/articles/64807-prophylactic-role-of-ivermectin-in-severe-acute-respiratory-syndrome-coronavirus-2-infection-among-healthcare-workers#!/
[Ivermectin cuts the spread of COVID by at least 77%] — Use of Ivermectin as a Potential Chemoprophylaxis for COVID-19 in Egypt: A Randomised Clinical Trial. Waheed M ShouMan1, abdelMoneM aWad hegazy2, RaMadan M nafae3, MouStafa I Ragab4, Saad R SaMRa5, dalIa anaS IbRahIM6, taRek h al-MahRouky7, aShRaf e SIleeM8. Journal of Clinical and Diagnostic Research. 2021 Feb, Vol-15(2): OC27-OC32. DOI: 10.7860/JCDR/2021/46795.14529. https://www.jcdr.net/articles/PDF/14529/46795_CE[Ra]_F(Sh)_PF1(SY_OM)_PFA_(OM)_PN(KM).pdf