[acdha]

There’s a big difference: we know antibodies are effective. That’s relatively well understood part of how the immune system works and it’s reasonable to assume that a high defensive response will translate into protection — not perfect, biology is complicated, but the most likely outcome is good.

Ivermectin, on the other hand, has no established mechanism which would make us expect it to work. It’s not impossible but given how only dodgy studies have shown beneficial effects by now it’d be a pretty big surprise to see benefits.