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Hospitals should be designated high-risk venues, staff should be tested twice a week, all patients should be vaccinated, and those who visit or are discharged should be subject to much closer monitoring.

These were the conclusions made by Ho Ching, CEO of investment firm Temasek, who took to Facebook on May 4 to weigh in about the largest currently-active Covid-19 cluster linked to Tan Tock Seng Hospital.

Analysis of cases in TTSH cluster

Taking reference from an infographic published in Lianhe Zaobao, Ho made the following observations about the 35 cases in the cluster, as of May 3:

• Of the nine healthcare staff in the cluster, five had been vaccinated, while four had not.

  • Two of the five vaccinated healthcare staff were symptomatic.
  • Three of the four unvaccinated healthcare staff were symptomatic.

This, Ho said, suggests that getting vaccinated offers protection as it results in milder illness, or even no symptoms.

Ho also pointed to the fact that vaccinated individuals have been found to be less likely to transmit Covid-19 as they would be carrying a lower viral load.

"Hidden datapoint": Relative risk of getting Covid-19 for vaccinated and unvaccinated individuals

Ho then presented what she called a "hidden datapoint", suggesting that it revealed how the risk of getting Covid-19 differed for vaccinated and unvaccinated individuals.

What if only 50 per cent of healthcare staff were vaccinated? 

Ho suggested a hypothetical scenario in which only 50 per cent of all healthcare staff had been vaccinated.

If this were the case, we might "conclude simplistically" that vaccination had little impact on whether someone would get infected with Covid-19, since nearly half of the infected healthcare staff were vaccinated, but still infected.

Furthermore, if vaccination among healthcare staff was indeed 50 per cent, Ho said, it would mean that vaccination only had the effect of making the illness milder.

Reality is that most healthcare staff are vaccinated

However, the reality, Ho said, was that healthcare staff had been mostly vaccinated.

Healthcare workers on the frontline were among the first to get vaccinated, from end-Dec. 2020.

If the vaccination rate was 80 per cent, it would mean that an unvaccinated individual was four times more likely to get Covid-19 as compared to a vaccinated individual.

This is because the number of healthcare staff in the TTSH cluster is roughly equal (five had been vaccinated, while four had not), even though there are larger numbers of vaccinated healthcare staff.

Thus, applying the same math, assuming the vaccination rate was 90 per cent, it would mean that an unvaccinated individual was ten times more likely to get Covid-19 as compared to a vaccinated individual.

Ho acknowledged that this was "a kind of back of envelope estimation," however, adding that specific data on the proportion of TTSH staff who were vaccinated would be needed for more accurate findings.

Both elderly and young patients at high risk of severe illness

Ho then made the observation that most of the patients in the TTSH cluster were elderly, and none of them had been vaccinated.

Covid-19 is known to cause higher rates of severe illness among the elderly.

However, even younger patients in hospitals would face higher risk of severe illness, Ho said, given that they would have other risk factors such as a separate illness.

This led her to make three policy suggestions.

1. Hospitals should be designated high risk areas, staff should be tested twice-weekly

Ho said healthcare staff worked in a "high potential superspreader vocation" given their repeated contact with patients, and the "high touch" nature of their work.

This makes them "no different from immigration and border related staff, or dorm residents".

Thus, Ho said, all healthcare staff should undergo antigen testing twice each week, which she said would be able to detect around 80 to 90 per cent of the Covid-19 cases.

Those who tested positive could then go through confirmatory PCR tests.

Such twice-weekly antigen tests would identify more infectious cases with high viral load, so they could be separated from the community to prevent further infections.

Antigen tests, Ho said, have advantages over PCR tests in the following areas:

• Affordability: Antigen tests cost about four to five times less.
• Speed: Antigen tests can produce results in 15 minutes, as compared to PCR tests which can take between three to six hours at their fastest, or even up to two to three days.
• Efficiency: Antigen tests would not reflect positive results for non-infectious cases which were shedding traces of the Covid-19 virus after they had recovered. This, Ho said, would help to reduce "unnecessary runaround".

2. All hospital patients should be vaccinated

Restating the point that none of the patients in the TTSH cluster had been vaccinated, Ho said that hospitals should adopt a "standard operating procedure" of offering all patients vaccinations.

She further suggested offering incentives, like reduced hospital charges of around five to nine per cent, particularly for patients who would have extended stays in the hospital.

"This reduces complications for both the patients themselves and the hospitals, and will reduce overall costs in time, money, anxiety and stress for everyone," said Ho.

3. Hospital visitors should be managed more closely

Ho's third and final suggestion was that hospital visitors should be managed more closely, offering nursing homes as a model.

According to Feb. 2021 updates to the precautionary measures by the Ministry of Social and Family Development (MSF), certain nursing homes could allow visitors, subject to a limit of two visitors per resident at a time, with a maximum of four pre-designated visitors per resident.

Visitors and residents are also required to abide by other precautions, such as wearing masks at all times during visits, which should take place at designated areas outside of living quarters and segregated from other residents.

The visits should also be limited to an hour or less.

"While we should welcome family visitors, so that patient morale and recovery is better, we should require certain visitor discipline," said Ho.

Vaccinated visitors should be allowed "more freely"

Ho also suggested that visitors who had been vaccinated should be allowed "more freely" as compared to unvaccinated ones.

Further, antigen testing should be done for unvaccinated visitors, as this would help reduce the risk of visitors bringing infections into the hospital, Ho said.

TTSH cluster

On May 4, five new cases were linked to the cluster at TTSH, bringing the total number of cases in the cluster to 40.

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Top image via HO Ching and TTSH on Facebook