My problem is how do you run a randomized trial with something as common as a deworming pill that is handed out in clinics by nurses and can be bought over the counter?
I am just curious.
Anyway, in this case, I do not believe deworming was as common as you assume:
> Baseline parasitological surveys indicated that helminth infection rates were over 90%, and over a third had a moderate-heavy infection according to a modified WHO infection criteria (Miguel and Kremer 2004)
> Drug take-up rates were high, at approximately 75% in the treatment group, and under 5% in the control group (Miguel and Kremer 2004).
5% of the population taking the drug when >90% should means the drug is not "common".