Have you lucky people who have been to Weh have taken malaria tablets when you went ?
I am going with my girlfriend (to lumba2) in a month or so and we're wondering ...
Cheers.
Jim.
Strictly medically speaking you should take malaria prophylaxis when travelling to Pulau Weh since it is classified as "highly endemic" (in contrast to Aceh which has a low endemicity) regarding the so-called tropical malaria (P. falciparum). It's true that prophylaxis cannot prevent malaria 100%, but the attack will be much less serious.
You also should take into consideration the location. I'm far from wanting to scare you, but if really you catch it and develop a serious malaria, it might become a bit difficult to get you from Gapang to a proper hospital in time (KL or Singapore).
Unfortunately, this is one of the few cases where it is not such a good idea to copy the locals, they never take any prophylaxis when they are in their habitual area. And they might have the parasites in the blood without being sick (which then might be transmitted).
Said that, there is also "reality". And I admit, when I was in Pulau Weh, I did not take any prophylaxis.
At the end of the day, you have to decide for yourself.
Other preventive measures, as listed by silent_running, are obviously as important as the prophylaxis itself.