A team of clinician-scientists from Singapore’s National University Health System (NUHS) has found that oral hydroxychloroquine and povidone-iodine throat spray are effective in reducing the spread of Covid-19 in high-transmission settings such as dormitories , cruise ships and prisons. Their findings, which were presented to the media on Friday, were based on a study of more than 3,000 migrant workers living in Tuas South Dormitory during the height of the Covid-19 outbreak in May last year. Hydroxychloroquine is a prescription drug used to treat malaria and arthritis while povidone-iodine throat sprays are over-the-counter medications that provide symptomatic relief of sore throat. Hong Kong-Singapore travel bubble to launch in May with vaccine restrictions The study, the largest on Covid-19 preventive therapy involving these drugs, was published in the International Journal of Infectious Diseases on April 14. Associate professor Raymond Seet, the study’s lead author, said only two methods besides vaccines have been effective in reducing the transmission of the coronavirus: wearing masks and social distancing. However, the study demonstrated the benefits of preventive therapy with either oral hydroxychloroquine and povidone-iodine throat spray in closed settings, both of which are easily available and safe for use. “This can represent a viable preventive strategy for individuals living in a closed and high-exposure setting, especially in areas and countries where Covid-19 vaccination is not available or widespread,” Seet said. At the height of the pandemic last year, some of Singapore’s largest coronavirus clusters emerged among the city state’s migrant workers, who are housed in dozens of crowded mega-dormitories. Concerns have recently emerged surrounding another dormitory outbreak, with 19 workers at Westlite Woodlands dormitory testing positive for Covid-19 last week. As part of the study, 3,037 migrant workers from Tuas South Dormitory aged between 21 and 60, with a mean age of 33, were recruited to participate in a randomised clinical trial. How did migrant worker dormitories become Singapore’s biggest coronavirus cluster? The dormitory was chosen for the trial as it was still in the early stages of the Covid-19 outbreak, said Seet, a senior consultant at the National University Hospital (NUH). Participating workers had no previous diagnosis of Covid-19, did not exhibit symptoms of respiratory illness and had negative serological tests for the coronavirus at the start of the study. These workers, who shared their rooms with non-participants, were spread over 40 floors of the dormitory, with each floor making up a “cluster”. Their rooms, which housed eight to 12 workers each, were also graded according to the risk of Covid-19 exposure. Unexposed rooms, for instance, had no confirmed Covid-19 cases prior to the trial. Each cluster was then randomly assigned to consume one of five types of medication for a period of six weeks. They were: Vitamin C (500mg daily) A combination of Vitamin C (500mg daily) and zinc (80mg daily) Povidone-iodine throat spray (270μg daily) Hydroxychloroquine (400mg once followed by 200mg daily) Ivermectin which is used to treat parasitic infections (12mg once) Seet said the medications were chosen to target the oropharyngeal space, which is the key entry point for viruses. As a widely used but unproven remedy during the pandemic, Vitamin C was picked as the medication against which the other drugs’ effectiveness would be compared. By the end of six weeks, 1,681 participants, or a little more than half, were diagnosed with Covid-19. Hong Kong-Singapore travel bubble: here’s what you need to know The frequency of infection was also significantly lower in participants who used hydroxychloroquine or the throat spray, compared to Vitamin C. The following were the infection rates for trialled medications: Vitamin C: 70 per cent infected (or 433 out of 619 participants) Hydroxychloroquine: 49 per cent infected (or 212 out of 432) Throat spray: 46 per cent infected (or 338 out of 735) Ivermectin: 64 per cent infected (398 out of 617) Vitamin C and zinc: 47 per cent (or 300 out of 634) Seet noted there was a “significant absolute risk reduction” of over 20 per cent for those who took hydroxychloroquine and throat spray. Although the cluster which consumed a combination of Vitamin C and zinc also had more than 20 per cent in absolute risk reduction, there was not enough statistical evidence to prove that the difference is not just due to luck, said associate professor Alex Cook from the National University of Singapore’s Saw Swee Hock School of Public Health. He was one of the 15 authors of the study. According to a press release issued by NUHS, the findings suggest povidone-iodine could create an environment within the oropharyngeal space relatively resistant to the coronavirus. A reduction in viral load could also reduce the exposure of virus particles to their close contacts during the incubation and asymptomatic phases of infection, interrupting transmission. When asked whether the findings show that the drugs could be used in another dormitory outbreak, Seet said the study was designed to address such situations anywhere around the world involving a closed, crowded, high-exposure setting. Read the original article at Today Online .