Aung P.L.Soe M.T.Soe T.N.Zhao Y.Cao Y.Aung P.P.Oo T.L.Lawpoolsri S.Nguitragool W.Sattabongkot J.Kaewkungwal J.Kyaw M.P.Parker D.M.Cui L.Mahidol University2025-08-242025-08-242025-08-01Open Forum Infectious Diseases Vol.12 No.8 (2025)https://repository.li.mahidol.ac.th/handle/123456789/111752Background. Plasmodium vivax poses a major challenge for malaria elimination, primarily because of relapse. Primaquine mass drug administration (PQ-MDA) has played a decisive role in eliminating vivax malaria in many temperate countries, but its efficacy in tropical/subtropical areas remains underexplored. Methods. We conducted a cluster-randomized crossover trial to determine the effect of PQ-MDA on P. vivax transmission in northern Myanmar, a subtropical area in the Greater Mekong subregion with perennial malaria transmission. Participants from two groups of villages (groups 1 and 2) were administered 0.25 mg/kg/day PQ base for 14 days as directly observed therapy. During PQ-MDA administration, each group alternated as the control while the other received the intervention, with the groups switching after 9 months. Clinical malaria incidence and prevalence were monitored to determine the efficacy. Results. PQ was administered in 541 participants in group 1 and 667 in group 2 during August–September 2019 and June–July 2020, respectively. In both groups, clinical P. vivax incidence sharply declined to zero within a month of PQ-MDA and remained vivax-free for almost a year. During round 1 PQ-MDA, group 1 with MDA had a significant reduction in the prevalence of subclinical P. vivax compared to group 2 as the control, with a model-adjusted odds ratio (aOR) of 0.46 [95% confidence interval (CI): 0.25–0.83]. During round 2, group 2 exhibited an even lower aOR of 0.15 (95% CI: 0.03–0.65) for subclinical P. vivax infection. Conclusions. PQ-MDA was effective in reducing both clinical and subclinical P. vivax infections in a subtropical, low-endemicity setting.MedicineArticleSCOPUS10.1093/ofid/ofaf4652-s2.0-10501325055023288957