Meltzer E, et al. - In order to assess the causal prophylactic efficacy of atovaquone-proguanil compared to other options for Plasmodium vivax, researchers performed a retrospective observational study, for 11 years, including Israeli rafters who had traveled to the Omo River in Ethiopia, a highly malaria-endemic area. They followed 252 travelers. Sixty-two (24.6%) travelers developed malaria. Among travelers using atovaquone-proguanil, 50.0% users developed late vivax malaria, as did 46.5% and 43.5% of mefloquine and doxycycline users, respectively; only 2 (1.4%) primaquine users developed late malaria. Findings thereby suggest short-course atovaquone-proguanil as effective in providing causal (liver schizont stage) prophylaxis for P. vivax, but as ineffective against late, hypnozoite reactivation–related attacks. Researchers recommend considering primaquine as the chemoprophylactic agent of choice for areas with high co-circulation of P. falciparum and P. vivax.