Efficacy of Focal Primaquine Mass Administration for Eliminating Plasmodium vivax Malaria in Northern Myanmar: A Cluster-randomized Trial

Background 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 (Group 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 nine 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%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. Conclusion PQ-MDA was effective in reducing both clinical and subclinical P. vivax infections in a subtropical, low-endemicity setting. This study was registered with ClinicalTrials.gov (NCT06392152).