SINGAPORE - The number of Covid-19 patients in intensive care units (ICU) here or requiring oxygen supplementation has tripled over the last two weeks, rising from eight in total on July 15 to 25 on Wednesday (July 28), with experts warning the number is likely to grow.

But they were quick to add that the healthcare system should be able to cope despite the worrying trend.

Professor Dale Fisher, senior consultant at the National University Hospital's (NUH) Division of Infectious Diseases, said there has been an increase in the number of unvaccinated people contracting the disease, after almost 1,000 new cases of Covid-19 were reported in the last week.

"Over that week, the number of unvaccinated cases in the older age groups has more than doubled, so I feel we can expect the numbers of new severe cases to increase significantly," he said.

But he added that the rise should still be "well within" the healthcare system's capabilities.

Health Minister Ong Ye Kung said on Wednesday that Singapore can open up about 1,000 ICU beds for critically ill Covid-19 patients. But he had also pointed out earlier that it takes only five weeks to overwhelm the hospitals' ICU capacity.

Prof Paul Tambyah, a professor of medicine at the National University of Singapore (NUS) Yong Loo Lin School of Medicine, said that with more than half the population here fully vaccinated, he anticipates one or two new severe cases a day if infections remain in the hundreds.

This estimate is based on the number of severe cases reported in other countries such as Britain and the United States where significant proportions of the population have been fully vaccinated, said Prof Tambyah, who is also a senior consultant at NUH's Division of Infectious Diseases.

Prof Teo Yik Ying, dean of the NUS Saw Swee Hock School of Public Health, noted that the number of infections reported daily is still above 100, with a number of cases among people above 70 years old who are unvaccinated or partially vaccinated.

"These are the ones that are at a high risk to experience severe disease and require hospital care," he said.

Two teams from the school have been carrying out modelling to predict which way the numbers might go - one led by Dr Hannah Clapham, an assistant professor at the school, and another by Associate Professor Alex Cook, who is vice-dean of research.

Prof Cook noted that vaccine uptake in the older age groups, who are at greatest risk, has risen to about 75 per cent.

Taking into account this statistic, as well as the effectiveness of the vaccines in preventing severe disease, the teams predicted that the risk of someone ending up in the ICU with Covid-19 has fallen from around 2 per cent to about 0.2 per cent.

This varies across age groups, Prof Cook clarified, as those under 40 have a much lower risk.

The 0.2 per cent figure could drop further if more seniors get their shots, he added.

Prof Fisher, who is also a professor of medicine at the NUS Yong Loo Lin School of Medicine, said a key factor in predicting the trend in terms of future severe infections is the rate of infection in unvaccinated people.

Prof Teo said another important factor is where community transmission takes place.

"For example, if present or new clusters emerge in areas frequented by the elderly or those with underlying medical conditions, then when these people are exposed and infected, that is when we start to see more medical complications arise," he explained.

But Singapore is "well prepared" for rising numbers of severe cases, said Prof Tambyah.

"We went through this last year and all the public hospitals, as well as many of the private hospitals have plans," he added.

Prof Fisher noted that while hospitals here have good capacity to deal with a surge in cases, they may need to postpone some functions such as elective work and clinics for a short while.

"If there was another hospital cluster, that would make service challenging. But we have got through such events before," he said.

Prof Teo said that Singapore already has the necessary capacity to handle a slight increase in severe cases.

"Our public hospitals monitor the utilisation of these resources very carefully, and we actually take a whole-of-country approach towards managing the usage of these resources," he said.

For example, when the required number of ICU beds was higher in mid-2020, the hospitals communicated with one another to identify available ICU spaces so patients could be sent there.

But he cautioned that if the number of those with severe illness spikes, stricter restrictions, which could include another circuit breaker, might be needed to break chains of transmission and allow hospitals to recover their capacity.

"This is really only a scenario that we will see when the spread enters vulnerable communities such as the unvaccinated elderly or unvaccinated people with underlying medical conditions," he said.

Prof Cook agreed, adding that there is a limit to how many beds in hospitals can be converted into ICUs.

"Potentially, if there are large outbreaks after we reopen, we may have to reimplement a temporary circuit breaker to safeguard the healthcare system, but the risk of this really depends on how many elderly Singaporean citizens and residents come forward for vaccination," he said.

He added: "Right now, the number of severe infections is much lower than at its peak early last year, thanks to the vaccine roll-out."