How Singapore moves forward in dealing and living with Covid-19 depends on the price the country is willing to pay to achieve this.

There is no perfect option, and it is a matter of choosing "the best set of trade-offs that we would wish to have", said Associate Professor Hsu Li Yang, an infectious diseases expert at the National University of Singapore's Saw Swee Hock School of Public Health.

He was one of three panellists at The Straits Times discussion, Living With Covid-19: When And How? on Thursday.

Prof Hsu said severe illness and deaths will rise as measures ease, but aiming for no deaths means the constraints on society will be extremely high: "We haven't talked about what we might want to accept in terms of the cost of living with Covid-19."

Singapore has close to 76,000 Covid-19 cases, with 90 people seriously ill and 14 in critical condition. A total of 59 people have died.

The nation can open up faster if it is willing to accept six or seven deaths a day. It may not be able to do that if it wants to keep the death toll closer to what one sees for influenza, which is two a day, he said.

Professor Ooi Eng Eong of Duke-NUS Medical School said at the discussion that Singapore's ability to keep deaths to less than 0.1 per cent - when in some countries the rate is as high as 3 per cent - is "extremely remarkable".

But the strict mitigating measures do cause other problems. To keep hospital beds free for Covid-19 patients, a lot of non-urgent treatments are being postponed.

Prof Ooi said: "Someone who needs a hip replacement because he can't walk - if we have to delay that, what would that do to his cardiovascular health when he cannot exercise?"

There are also non-health costs, he said. "Our children are growing up in a situation where going to school is just about education. There is no play, and play is so important in growing up.

"Part of the benefits of university education is that you form this network that then carries you through your career. Our university students have been stuck at home for a year and a half, so what is that going to do to the future of our next generation?"

Professor Leo Yee Sin, executive director of the National Centre for Infectious Diseases (NCID), said Singapore has done very well so far in keeping the death rate in check.

But she added: "Beyond the healthcare system, there is the entire ecosystem, the economy and many other conditions that you have to consider.

"That is again, another very delicate balance. You open too soon, you are too relaxed, you have to deal with a surge. If you are too restrictive, you are going to suffer a lot in terms of your other areas, not just healthcare."

Prof Leo said there are still many unknowns about Covid-19: "Whatever we had predicted last year... we thought we knew so much about coronavirus, how coronavirus would behave... we were totally wrong."

The game changer was the advent of the highly transmissible Delta variant of the coronavirus this year. Its shorter incubation period gives our bodies less time to mount a defence, which means that vaccines are less effective in reducing infections.

The Delta variant behaves very differently from the ancestral virus, Prof Leo said, and this has implications. "We cannot continue to hold on to the preset planning, we have to change and evolve along the way, how we move (forward). The virus will evolve and will impact our lives."

So, there will be no herd immunity against Covid-19 no matter how high the vaccination rate, and measures that were effective last year may not work any more, the experts warned. There could be more changes and surprises in store, they added.

Prof Ooi said what is needed is to learn as much as one can about the disease, the same way the nation learnt to deal with dengue. In 2005, four in five dengue patients in Singapore were hospitalised, depriving other patients of a hospital bed.

But Singapore's doctors have since developed "a predictive algorithm to see who really needs to be in hospital", so even though Singapore had 35,000 dengue cases last year, the highest ever, hospitals were not overwhelmed.

What is critical now, said Prof Leo, is for people with even mild symptoms to get tested and to get treated early if they have Covid-19.

"Once you develop symptoms, which is when your oxygen level is down, that would be the best time to intervene, and (it is important) we don't miss that most critical point," she said.