SINGAPORE - All 62 Covid-19 cases detected among migrant workers from the North Coast Lodge dormitory in Woodlands on Monday (Aug 23) were fully vaccinated, said the Ministry of Manpower (MOM) on Tuesday.
The first three cases were detected through rostered routine testing, which also coincided with wastewater tests signalling positive results, said MOM in response to queries from The Straits Times.
Wastewater testing looks out for Covid-19 viral fragments that are shed by individuals in their stool.
It complements rostered routine testing in dormitories for early detection of Covid-19 transmission, and this facilitates intervention and the isolation of cases.
The remaining cases at the dormitory were detected through pre-emptive testing.
"All of them were fully vaccinated, and were either asymptomatic or had mild ARI (acute respiratory infection) symptoms. They have been moved to a healthcare facility for further care and treatment," said MOM.
Close contacts of the 62 confirmed cases have also been isolated, and safety time-out notices have been issued by the Building and Construction Authority to work sites where the infected workers had been working, added the ministry.
All residents of the dormitory will also be tested frequently over the next few weeks.
On Tuesday, the Ministry of Health said that there were 24 new cases linked to the North Coast Lodge cluster, bringing its size to 86. Testing operations at the dormitory have been completed, with only 12 test results still pending.
In all, more than 5,300 residents were tested for Covid-19 over the past three days.
As a precaution, all residents at the dormitory have been placed under a movement restriction order.
Under the order, workers must remain in their rooms for 14 days while the necessary investigations and clinical assessments are carried out.
They must also adhere to safe living measures and maintain strict safe distancing while remaining within their rooms.
MOM did not respond to queries about how many of the dorm's residents have been fully vaccinated against Covid-19, and when the movement restriction order will end.
As at Aug 3, more than 90 per cent of migrant workers in dormitories have been fully vaccinated, said MOH's group director of crisis strategy and operations group, Mr Dinesh Vasu Dash.
To help contain the spread of Covid-19, the Assurance, Care and Engagement (ACE) Group under MOM continues to enforce safe living measures at the dormitories, and maintain tight surveillance on migrant workers with ARI symptoms.
Asked if the rising number of cases could lead to a similar Covid-19 outbreak in dormitories as last year's, Professor Teo Yik Ying, dean of the National University of Singapore's Saw Swee Hock School of Public Health, said: 'The high-density nature of dormitory living means there is always a risk of large-scale outbreaks within a dorm, whenever anyone in there is infected."
He expects more cases to emerge over the next few days as surveillance testing is conducted there, though the risk of the workers developing severe symptoms is "extremely low" as many are younger and in good health to begin with.
His colleague, Associate Professor Hsu Li Yang, vice-dean for global health, and infectious diseases programme leader, however, said that while there will likely be more dormitory outbreaks in the near future, the 90 per cent vaccination rate would mean that the outbreaks will not be of a similar scale to the ones seen last year.
However, the fact that many workers were mildly symptomatic could mean that the workers themselves might not have realised that they have been infected, said Prof Teo.
"This can lead to more infections as the infected cases move about in the dorms, albeit their movements within the dorms are already quite curtailed," he added.
In addition, while safe living measures and protocols can generally prevent large outbreaks from happening, the transmissibility of the Delta variant of Covid-19 puts a "practical limit" to how much the outbreak can be confined, said Prof Teo.
Prof Hsu said: "When the workers continue to live in close quarters in dormitories with up to 10 persons per room and communal toilets, safe living measures alone will merely mitigate but not prevent significant transmission of Covid-19 in the dormitories."