The effect size was very large. The calculated p-value was <0.0001.

https://www.pfizer.com/news/press-release/press-release-deta...

To mention it, not necessarily directed at you. Larger test groups are required when trying to distinguish between less effective treatments.

If rabies has a 99% death rate and you try your rabies treatment on 10 people, 9 of whom live, that's much stronger evidence than a situation where 50% of people died without treatment versus 48% with treatment (sample size 100). To be confident it's not just random chance, you'll need a really large sample size for the 2nd situation.

Depending on the effect severity you can get a representative sample from as low as 40 people (not necessarily in this case).

That's not low for the effect size they're observing. Note that this is a phase 2/3 trial. The safety trials have already occurred.

This is a randomized clinical trial; participants are recruited into the study using methods that eliminate the biases associated with self-selected participation, like internet or TV polls. You can get statistically valid results from small samples, that apply to very broad populations, using this methodology.

Gotta prove it with 1200 before you get the funding for 10,000.