Recurrence rate of vivax malaria in the Republic of Korea

In the Republic of Korea (ROK), military antimalarial chemoprophylaxis was initiated in 1997. Although chemoprophylaxis reduces malaria cases, long-term chemoprophylaxis could increase resistance. In this study, the recurrence rate of vivax malaria was investigated. All vivax malaria cases that occurred before 31 December 2003 among soldiers and veterans who entered the ROK army between 1 January 1998 and 28 February 2001 were reviewed. Of the 3881 reported cases (2375 soldiers and 1506 veterans), 62 (1.6%) experienced a second attack and 2 (0.05%) experienced a third attack. Fifteen cases (24.2%) recurred ≤60 days and 43 cases (69.4%) recurred >180 days after the start of initial treatment. Most of the second attacks (54/62) were exposed to malaria risk after initial treatment. Among 1506 veterans, 5 (0.3%) recurred and they had not been exposed to malaria risk after retirement; 1 recurred 43 days and 4 recurred >180 days after the start of initial treatment. All recurring cases were completely cured using the same dosage and regimen used for the first or second treatments. In conclusion, few cases of vivax malaria recurred after standard treatment. It is suggested that recurrences of vivax malaria are effectively prevented by the current treatment regimen and dosage.