Seet RCS, Quek AML, Ooi DSQ, et al. - Researchers investigated the efficacy of existing licensed pharmacotherapies in reducing the spread of coronavirus disease 2019 (COVID-19). In this open-label parallel randomized controlled trial, healthy migrant workers quarantined in a large multi-storey dormitory in Singapore (each defined as individual floors of the dormitory) were randomly assigned in forty clusters to receive a 42-day prophylaxis regimen of either oral hydroxychloroquine (400 mg once, followed by 200 mg/day), oral ivermectin (12 mg once), povidone-iodine throat spray (3 times/day, 270 µg/day), oral zinc (80 mg/day)/vitamin C (500 mg/day) combination, or oral vitamin C, 500 mg/day. Overall findings suggest superiority of chemoprophylaxis with either oral hydroxychloroquine or povidone-iodine throat spray relative to oral vitamin C in reducing SARS-CoV-2 infection in young and healthy men. Participants well tolerated oral hydroxychloroquine and povidone-iodine throat spray use. No significant difference in infection rates was observed with oral ivermectin and zinc/vitamin C.