Analisis efektifitas-biaya pengobatan Malaria Vivax di Puskesmas Koba, Kabupaten Bangka Tengah, Propinsi Kepualuan Bangka Belitung tahun 2006 = Cost effectiveness analysis of drug therapy of Malaria Vivax in Koba community helath center, District of Bangka Tengah, Province of Bangka-Belitung archipelago in 2006