Blood stage of Plasmodium vivax in central China is still susceptible to chloroquine plus primaquine combination therapy.

In central China, Plasmodium vivax accounts for all of the native reported cases of malaria. Chloroquine (CQ) plus primaquine (PQ) have been used for more than 60 years as the frontline drugs, but the risk of treatment failure remains unknown. To measure the effectiveness and safety of CQ-PQ among vivax malaria patients, a total of 39 subjects with monoinfection vivax malaria was enrolled in a study from 2008 to 2009. There were no recrudescence or danger signs observed within the 28-day follow-up period, showing that blood stage of P. vivax isolates from central China is still susceptible to CQ plus PQ combination therapy. However, the antirelapse efficacy of PQ is difficult to assess because of the high rate of loss to follow-up after 28 days; also, parasites persisted in a single case at 3 days post-antimalarial drug treatment, indicating that continuous annual monitoring is needed in central China.