SINGAPORE - Although the number of active Covid-19 clusters here crossed the 100 mark on Tuesday, the increasing vaccination rates provide a defence against the rising number of cases, said experts.

Instead, the main metrics should be shifted to focus on the number of severe Covid-19 cases and deaths.

The high number of active clusters and new infections is not as worrying, now that 62 per cent of the population is fully vaccinated, with another 15 per cent having received their first dose, said Professor Teo Yik Ying, dean of the National University of Singapore's Saw Swee Hock School of Public Health.

The last time Singapore had such a high number of active clusters was during the outbreak in the migrant worker dormitories last May. There had been more than 90 active clusters then.

"We can see that despite the high number of daily reported cases, as well as the number of active clusters, the ICU utilisation remains very modest and we do not have too many people in the hospital requiring oxygen supplementation," said Prof Teo.

Vaccination may not prevent people from getting Covid-19, but it significantly reduces the risk of an infection developing into a severe illness.

Associate Professor Alex Cook, who is vice-dean of research at the same school, said that although the number of severe cases has edged up, "it is far below the level" it was in March and April last year, when there was widespread community transmission.

There were 31 cases in intensive care in April last year, compared to the present seven cases as at Tuesday (Aug 3).

Prof Dale Fisher, a senior diseases expert at the National University Hospital, said: "As we approach 80 per cent immunity by the end of the month, I would expect there to still be many cases, but the number of new severe cases should plateau as more become immune."

He noted that there is also a real possibility that Singapore will enter "endemic policy mode" before the number of cases and clusters are reduced to levels of a few months ago.

This is a result of the higher transmissiblity of the Delta variant, and the vaccination level of the population, making silent spread of the disease much easier.

Prof Teo said it would, however, be more concerning if these active clusters are in locations that are frequented by the elderly, or those with underlying medical conditions, as these groups of people are at risk of severe disease.

He noted that around 20 per cent of those aged 70 and above have not been vaccinated thus far.

In addition, Prof Cook said that cases in clusters are inherently less of a problem compared with unlinked cases - as those linked to clusters are already under surveillance or quarantine, and are thus less likely to seed new infections.

"This is particularly so for household clusters because the household members are typically exposed to the same index, which lessens the total number of people at risk," he said.

However, it is more worrying if there are households with elderly members who have not been vaccinated, thinking that they would not be at risk if they do not go out much, added Prof Cook.

"That is not the case. Even if the family members are vaccinated, they could still bring infection back into the household, even if they themselves have no, or only mild, symptoms," he said.

Prof Teo advised everyone from households with unvaccinated people, especially seniors, to be prudent with their social interactions and movements in public, forming a protective "social bubble" to minimise exposure to the virus.

He also pointed out that a high number of clusters is an "indirect consequence" of high vaccination rates, as vaccinated people have few to no symptoms, and may not realise they are infected when they go about their daily activities.

"While a vaccinated person is less contagious when infected, there is still the small chance of infecting others, and this is when new transmission chains, or clusters, may be seeded in the community," said Prof Teo.

Prof Paul Tambyah, president of the Asia Pacific Society of Clinical Microbiology and Infection, said that as the number of vaccinated people goes up, the number of new clusters will likely drop and the older clusters will close naturally.

"The concern is for hidden communities like last year's migrant workers living in dormitories, and this year's elderly cleaners and KTV hostesses," he said.

There are many short-term visit pass holders who are not yet eligible for vaccinations who may be a hidden reservoir of infection that cannot be ignored, he noted.

Prof Cook said: "We need to stop agonising over the number of cases and clusters. As we move into the endemic state, outbreaks and clusters will occur, but because most of the population is protected through vaccination, few of these infections will progress to severe disease."