Evaluation of the efficacy of chloroquine chemoprophylaxis for vivax malaria among Republic of Korea military personnel.

Chloroquine has been used massively for vivax malaria prophylaxis and treatment in the Republic of Korea (ROK) military personnel from 1997. Although prophylaxis is generally regarded as successful among ROK military, prophylaxis failure has been repeatedly reported. Before the prophylaxis program was started on July 4th 2011, which was completed on October 16th 2011, by the ROK military, more than 60% of malaria cases were attributed to new infection or long-latency relapse. During the prophylaxis program, the authors re-examined the efficiency of chloroquine chemoprophylaxis in ROK military during the last 6 months of 2011 by measuring compliance and whole blood chloroquine levels in 41 malaria patients immediately before instituting antimalarial therapy between July and December. Three patients (7.3%) showed good compliance, and had whole blood total chloroquine levels above the minimally inhibitory concentration (100 ng/mL). However, 28 (69.3%) of these 41 patients when admitted to hospital showed poor or no compliance with prophylaxis; 4 of the 28 (14.3%) were stationed outside the mass prophylaxis region, and 5 (17.9%) subjects were infected after the prophylaxis program had finished. These findings indicate that the current malaria control program should be carefully reconsidered, in terms of, individual instruction, current chemoprophylaxis program regimens, and schedules to improve the efficacy of prophylaxis in the ROK military.