SINGAPORE, April 26 — A team of clinician-scientists from the 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 (April 23), 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 dormitories 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.

The study is the largest done so far internationally on Covid-19 preventive therapy involving these drugs. It was published in the International Journal of Infectious Diseases on April 14.

Advertisement

Why the study matters

Speaking during a brief to the media on Friday, the study’s lead author Associate Professor Raymond Seet said that besides the vaccine, only two methods so far have proven effective in reducing the transmission of the coronavirus — wearing masks and social distancing.

However, this is the first study to demonstrate 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.

Advertisement

“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,” he added.

How the study was done

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.

The dormitory was chosen for the trial as it was still in the early stages of the Covid-19 outbreak, said Assoc Prof Seet, who is a senior consultant at the National University Hospital (NUH).

Speaking during a brief to the media on Friday, the study’s lead author Associate Professor Raymond Seet said that besides the vaccine, only two methods so far have proven effective in reducing the transmission of the coronavirus — wearing masks and social distancing.

However, this is the first study to demonstrate 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,” he added.

How the study was done

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.

The dormitory was chosen for the trial as it was still in the early stages of the Covid-19 outbreak, said Assoc Prof Seet, who is a senior consultant at the National University Hospital (NUH).

Key findings

By the end of six weeks, 1,681, or a little over half, of the participants were diagnosed with Covid-19.

The frequency of infection was also significantly lower in participants who used hydroxychloroquine or the throat spray, compared to Vitamin C.

The following are 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)

Assoc Prof Seet noted that there was a “significant absolute risk reduction” of over 20 per cent for those who took hydroxychloroquine and throat spray.

While 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 Assoc Prof 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 that povidone-iodine has the potential to create an environment within the oropharyngeal space which is relatively resistant to the coronavirus.

A reduction in viral load could also possibly reduce the exposure of virus particles to their close contacts during the incubation and asymptomatic phases of infection, thus interrupting the virus’ transmission.

What the findings mean

The results of the study come as concerns emerge over another dormitory outbreak, with 19 workers at Westlite Woodlands dormitory testing positive for Covid-19 last week.

When asked if the findings show that the drugs can be used in another dormitory outbreak, Assoc Prof Seet said that this study was designed to address such situations anywhere around the world where there is a closed, crowded and high-exposure setting.

On whether there could be long-term side effects from using these medications, Dr Paul Tambyah, who is one of the authors of the study, pointed out that throat spray is already available over the counter. This means that it is safe and has no significant, long-term side effects.

Likewise, doses of hydroxychloroquine used during the study were lower than that usually administered for arthritis. In this regard, the study has shown that it is safe for use, added Dr Tambyah, who is senior consultant at NUH. — TODAY