Guys wearing steel pots in Vietnam took it daily for the same reason. I was one of them. No side effects....No malaria.
I remember in Vietnam we took one little white anti-malaria pill daily and one big orange pill once a week.
No side-effects from quinine? Oh my goodness. I remember when I had tropica malaria I had to take quinine. It made me so dizzy that I could only lie on the floor, forget about sitting or walking anywhere. Even so, I kept feeling as if I would fall off. Then, I would hear symphonies playing on crystal instruments, all at once. I had to take an anti-nausea medicine 30 minutes prior to my quinine so I could keep it down. Quinine definitely had some amazing side-effects.