[Imnimo]

I'm not an expert, but my understanding is that the error bars on efficacy for the single dose are quite large, just because of how the studies are conducted. Moderna's lower bound was below 70% with a single dose, and Pfizer's is below 30%. That's not to say that a single does is definitely not effective, just that there's a lot more uncertainty, and so the bounds are much looser. We also don't know whether giving a second dose a few months later rather than a few weeks later would work as well.

Depending on supply forecasts, it might be worth running a new trial to get a better handle on the efficacy of a single dose, but going that route now would definitely be a gamble. Especially since we're formulating this single dose hypothesis after having run the experiment and seen the results, which is always a dangerous approach.

Still, the data do seem to suggest that it's very plausible that a single dose would be sufficient. If things get bad enough, or supply is low enough, maybe that's a gamble worth taking.