SINGAPORE: A type of antiseptic throat spray, as well as an oral drug usually prescribed to treat malaria and arthritis, have been found to be effective in reducing the spread of COVID-19 in high-transmission settings, said Singapore researchers on Sunday (Apr 25).

The findings were made after a large-scale clinical trial conducted last May, involving more than 3,000 migrant workers living in Tuas South dormitory.

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).

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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.

HOW THE TRIAL WAS CONDUCTED

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

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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. 

Enrolment took place in May last year amid a “slow but steady increase in (COVID-19) numbers”, at the dormitory, Dr Seet said. 

It was publicised to dormitory residents from countries like India, Bangladesh, China and Myanmar.

Large-scale NUHS clinical trial on preventing covid-19 infection

A translator explains the study protocol, highlighting the voluntary basis of participation. (Photo: National University Health System)

Forty clusters, each defined as individual floors of the dormitory across five blocks, were randomly assigned to receive a six-week regimen. 

Two groups were each given the two drugs, while another group was given ivermectin, a drug typically used to treat parasitic diseases. 

Another group was given a combination of zinc and vitamin C. The control group was given vitamin C in place of a placebo.

The povidone-iodine throat spray had to be used thrice a day. 

THE RESULTS

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,” Dr Seet said.

This was after adjustments were made for “potential confounders”, like nationalities and compliance to medications. 

“This is a very simple intervention with virtually minimal side effects where we could actually cut the transmission rates in a meaningful way,” Dr Hartman said.

THE IMPLICATIONS

The drugs can complement other preventive measures in high-risk settings, said researchers.

“Such settings include cruise ships, prisons, refugee camps and meat processing facilities, where there may be a pressing need for additional means to prevent spread,” Dr Seet said. 

Prof Tambyah gave the example of an outbreak in a nursing home.

“It’s not something we are recommending across the board … If there’s an outbreak, then certainly that is something that’s worth considering,” he said.

Researchers stressed that the drugs are not meant to be used for COVID-19 prevention in the general community if it is a lower-risk setting. 

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