You can easily get the information online from several different Government agencies (UK, US, Australia). The UK considers North Sulawesi low risk (but Halmahera is high risk). As I recall I did not use malarone (which is what I typically use, have never had any problems and have had vertigo in the past, YMMV) in Sulawesi (where I was in the jungles) but did on Halmahera. This is from the UK (NHS) - "antimalarial tablets are not usually recommended, however, they can be considered for certain travellers who may be at higher risk e.g. longer stay in rural areas, visiting friends or relatives, those with medical conditions, immunosuppression or those without a spleen" for areas classed as low risk. Especially try to avoid being bitten between dusk and dawn. US is a bit more vague. Malaria incidence in most of the region, and even in Halmahera has been going down in recent years. But, with anything, it is a risk decision. Malaria can be exceptionally nasty, so one has to decide how much risk they are willing to take.