Thankfully, the UK went ahead and carried out a large-scale randomized controlled trial in the middle of the pandemic anyway despite the difficulty - otherwise

Thankfully, the UK went ahead and carried out a large-scale randomized controlled trial in the middle of the pandemic anyway despite the difficulty - otherwise we'd all be completely in the dark. Unfortunately, we seem to be pretty much the only country which did, which means that the evidence available is limited to the treatment and dosage combinations that happened to be included in that trial.