An antiseptic throat spray and an oral drug usually prescribed to treat malaria and arthritis have been found to effectively reduce the spread of COVID-19 in high-transmission settings, researchers in Singapore have found, according to a media report on Sunday.

The findings were made based on a large-scale clinical trial conducted last May, involving more than 3,000 migrant workers living in Tuas South Dormitory in the Industrial District of Singapore, Channel News Asia reported.

During the six-week trial, workers were given a povidone-iodine throat spray, which can be bought off the counter, and oral hydroxychloroquine, which requires a prescription.

Both were found to reduce the incidence of coronavirus infection, according to the study.

“This is the first study to demonstrate the benefits of prophylactic, or preventive therapy with either oral hydroxychloroquine or povidone-iodine throat spray in reducing SARS-CoV-2 infection among quarantined individuals living in a closed and high exposure setting," said lead author of the clinical study, Associate Professor Raymond Seet from the National University Hospital (NUH).

The two drugs were chosen because they are easily available, said Dr Seet. He also noted that they protect the throat, the “key entry" for viruses.

He was presenting the study at the National University Health System and was accompanied by co-investigators Professor Paul Tambyah, Associate Professor Mikael Hartman, Associate Professor Alex Cook and Assistant Professor Amy Quek.

The findings have been published in the International Journal of Infectious Diseases.

A total of 3,037 asymptomatic healthy men aged between 21 and 60 were involved in the trial on a voluntary basis.

Participants were excluded if they had any symptoms of respiratory illnesses like fever, cough or loss of smell a month before the start of the trial. Those who had previous COVID-19 infection were also not included.

The povidone-iodine throat spray had to be used thrice a day. After six weeks, more than half of the participants had tested positive for COVID-19.

But among those who used the throat spray, only 46 per cent contracted the disease. This is compared to 49 per cent among those who took hydroxychloroquine and 70 per cent who took vitamin C.

“We concluded that povidone-iodine throat spray was associated with a statistically significant reduction in infection by an absolute risk of reduction of 24 per cent while oral hydroxychloroquine was associated with a statistically significant reduction in infection by an absolute risk of reduction of 21 per cent," the channel quoted Dr Seet as saying.