Ivermectin Looks Good for COVID-19 Prophylaxis

Early on in the pandemic, Ivermectin was one of the few interventions that seemed promising, but since then I'd seen mainly negative headlines about faked pro-Ivermectin data, so I implicitly categorized it with hydroxychloroquine as a discredited hypothesis. But in response to my recent blog post on Machiavellian attitudes towards informing the public, ChristianKl from LessWrong asked me why I hadn't mentioned Ivermectin along with vitamin D. After a quick Google Scholar search, I found that the evidence for it seems surprisingly strong.

Kory et al cite 3 RCTs testing Ivermectin as a prophylactic for people at high risk of getting COVID (hospital workers and family members of people who recently tested positive). One of the three is by Elgazzar who faked his data, but the other two also find strongly statistically significant reductions in COVID infection rates. The effect size is huge; in both studies infections were around 90% lower in the treatment group.

The papers cited for the RCTs seem sketchy - neither describes the assignment method clearly and one confusingly uses the word "observational" to describe what otherwise seems like an intervention study. But Kory et al also cite some pretty good looking confirming observational data showing similar-sized effects, and according to LessWrong it looks like there is weak independent evidence that Ivermectin also helps people who already got COVID, when you exclude studies known to be fake.

This isn't as clean as the case for vitamin D but it seems like it might be worth taking if you're at high risk. Side effects seem a lot milder than the vaccines but not as mild as vitamin D, and the level of protection seems broadly comparable.

The hospital worker RCT gave the treatment group 12mg monthly. The RCT for relatives of someone who tested positive gave the treatment group .25 mg/kg twice, once as soon as the positive test was revealed, and again 24 hours later. So I'd plan to take 12mg monthly if the Delta wave takes off in NY, and one extra dose if any of my housemates or other close contacts tests positive.

Like with any new drug I looked up drug interactions & side effects to make sure I wasn't gonna hurt myself.

UPDATE 17 November 2021

Astral Codex Ten points out the obvious mechanism for Ivermectin prophylaxis: parasitic worms compete for immune priority with viruses. In places with endemic parasitic worm infestations, such as the places in the RCTs that found huge effects, low-impact deworming could easily improve resistance to COVID. This implies that people in countries like mine with very limited worm problems shouldn't bother, but if you live in somewhere like Egypt, Bangladesh, or Rancho Vista, TX, a global pandemic might be an especially important time to get your hands on some Ivermectin.

I feel silly about not having figured this out earlier. I even specified the general mechanism in an exchange with a malicious idiot on Twitter, I just didn't notice the worms connection.

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