| Shrnutí: | <p><strong>Background:</strong> Mass administrations of antimalarial drugs (MDA) have reduced the incidence and prevalence of <em>P</em>. <em>falciparum</em> infections in a trial in the Greater Mekong Subregion. Here we assess the impact of the MDA on <em>P</em>. <em>vivax</em> infections.</p>
<p><strong>Methods:</strong> Between May 2013 and July 2017, four villages in each Myanmar, Vietnam, Cambodia and Lao PDR were selected based on high prevalence of <em>P</em>. <em>falciparum</em> infections. Eight of the 16 villages were randomly assigned to receive MDA consisting of three-monthly rounds of three-day courses of dihydroartemisinin-piperaquine and, except in Cambodia, a single low-dose of primaquine. Cross-sectional surveys were conducted at quarterly intervals to detect Plasmodium infections using ultrasensitive qPCR. The difference in the cumulative incidence between the groups was assessed through a discrete time survival approach, the difference in prevalence through a difference-in-difference analysis, and the difference in the number of participants with a recurrence of <em>P</em>. <em>vivax</em> infection through a mixed-effect logistic regression.</p>
<p><strong>Results:</strong> 3,790 (86%) residents in the intervention villages participated in at least one MDA round, of whom 2,520 (57%) participated in three rounds. The prevalence of <em>P</em>. <em>vivax</em> infections fell from 9.31% to 0.89% at month 3 but rebounded by six months to 5.81%. There was no evidence that the intervention reduced the cumulative incidence of <em>P</em>.<em>vivax</em> infections (95% confidence interval [CI] Odds ratio (OR): 0.29 to 1.36). Similarly, there was no evidence of MDA related reduction in the number of participants with at least one recurrent infection (OR: 0.34; 95% CI: 0.08 to 1.42).</p>
<p><strong>Conclusion:</strong> MDA with schizontocidal drugs had a lasting effect on <em>P</em>. <em>falciparum</em> infections but only a transient effect on the prevalence of <em>P</em>. <em>vivax</em> infections. Radical cure with an 8-aminoquinoline will be needed for the rapid elimination of vivax malaria.</p>
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