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COVID-19: Singapore commissions 3 studies to determine extent of infection in population

Singapore is believed to be among the first countries in the world to conduct such tests on a large scale. (PHOTO: Getty Images)
Singapore is believed to be among the first countries in the world to conduct such tests on a large scale. (PHOTO: Getty Images)

SINGAPORE — A COVID-19 research workgroup in Singapore has commissioned three studies to determine how much of the population is infected by the coronavirus, and to understand how different segments of the population have been affected by it.

The National Centre for Infectious Diseases (NCID), which is spearheading this workgroup, said in a news release on Wednesday (29 April) that the studies will be done via seroepidemiology – using antibody-based tests to identify the population segments, and the size of segments, that have been exposed to COVID-19.

According to NCID, the studies will be valuable for:

  • Accurately comparing data across different groups of people (age or geographic region), which will help in understanding the factors which determine the effectiveness of COVID-19 control measures in the long run;

  • Identifying the population segments that remain susceptible to being infected, and would benefit from a vaccine;

  • Giving insight into under-diagnosed mild cases – often young, healthy individuals – such as the extent to which such cases are untested, and how they may contribute to the spread of COVID-19.

Singapore is believed to be among the first countries in the world to conduct such tests on a large scale.

“Rigorous research is critical to ensuring a coordinated, effective national-level outbreak response. In the case of COVID-19, of which much remains unknown, a swift response in clinical aspects as well as research is especially crucial to outpace the virus’ rapid spread,” said Professor Leo Yee Sin, NCID’s executive director and chairperson of the research workgroup.

Study #1: on residual sera

The first study is to measure how widespread COVID-19 infection is in within the community, given how some of the infections are mild or with no symptoms especially for children.

Conducted by NCID and the Duke-NUS Medical School, the study is based on leftover blood samples from people who had their blood taken as part of routine care. While this method has been used to assess antibody levels in other infectious diseases, this is the first time it is being done for COVID-19.

Already, 774 samples have been tested across adults and children, but none have met the criteria of being tested positive for COVID-19. This shows that COVID-19 exposure in the community is extremely rare, and there is no widespread community transmission as of the last two weeks of March.

“At this critical juncture, it is important to know the extent of COVID-19’s exposure in the community, given potential asymptomatic infection and herd immunity,” said Professor Wang Linfa, director of Emerging Infectious Diseases Programme at Duke-NUS Medical School.

Study #2: on persons at high risk of COVID-19 exposure

The second study will reach out to about 2,000 household and close contacts of COVID-19-positive persons to estimate the number of asymptomatic infections and determine the risk factors of COVID-19 exposures.

Participants will answer a risk questionnaire and donate a blood sample for antibody testing.

Full results are expected to be available in two months, and they may offer a better understanding of asymptomatic infections and facilitate more effective risk assessments and better estimates of fatality rates.

In addition, determining the risk factors can offer insight into how COVID-19 is transmitted, thereby better informing policies and guidelines to stop its spread.

So far, the study has received results from about 300 participants. They show that 2.5 per cent had antibodies which indicate that they were infected with COVID-19, despite not having a positive test during the time they were quarantined.

In combination with the 2.7 per cent who tested positive for the virus during their quarantine, this indicates that about 5 per cent of household members were eventually infected after the initial COVID-19 case from that household was diagnosed. Of these, half would be asymptomatic or minimally symptomatic.

Study #3: on exposure and infections among healthcare workers

The third study will assess the extent of COVID-19 exposure and infections among healthcare workers in Singapore.

It is currently being undertaken at NCID, Tan Tock Seng Hospital and National University Hospital, and will involve frontline staff in direct contact with COVID-19 patients, hospital staff working in non-COVID-19 patient care, as well as support staff.

Close to 1,100 healthcare workers have been enrolled voluntarily in the study, which will be conducted over six to 18 months, and will help evaluate the impact of COVID-19 exposure and whether current measures to protect the healthcare workers are adequate.

Initial results from antibody testing between February and early April suggest that none of the healthcare workers had COVID-19 infection at the time they joined the study. The gives strong evidence that infection control and prevention procedures have been adequate to protect frontline healthcare workers.

The study follow-up is expected to continue until the third quarter of 2021. Results will be shared with the Ministry of Health as well as the local and international infection control and prevention community, to further improve upon current protection measures for healthcare workers.

All tests carried out at Duke-NUS lab

All studies are based on standardised tests of blood samples for antibodies to SARS-CoV-2 – the strain of coronavirus that causes COVID-19 – which are carried out in a single laboratory at Duke-NUS Medical School. This allows for valid comparisons across different populations despite different sampling methods.

The studies were formulated in January, soon after COVID-19 started spreading outside China.

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