BackgroundThe relocation of Indonesia's capital to Ibu Kota Nusantara (IKN) in East Kalimantan, a malaria and dengue hotspot, presents new risks of infectious disease transmission due to land-use changes and population movements. Current knowledge on the impact of these changes on vector-borne diseases, especially Plasmodium knowlesi malaria and other arboviruses, is limited. Serological surveillance offers a robust method for assessing population exposure.MethodA community-based cross-sectional study will be conducted in IKN and its surrounding area, in East Kalimantan. Approximately 2,000 individuals aged >1 year will be enrolled. Finger-prick blood samples will be collected for serological analysis (multiplex bead-based assays for malaria species, and dengue virus serotypes) and malaria RDTs. Demographic, clinical, environmental, and geolocation data will also be collected. Statistical and geostatistical models will be used to assess seroprevalence, spatial patterns, and risk factors of exposure to malaria and dengue.