I spoke to a few folks in India, and seems like the majority are on some form of maintenance dose of chroloquine from a getting malaria in the last 6-8 months. I hear this is pretty common practice there.
And not just OTC, but handed out for free and in large quantities at govt hospitals.
I am living in India right now and have never heard about this. It is interesting that you would gather that the majority of us are on some dose of Chloroquinine. Nobody I know, is.