SINGAPORE - Questions on vaccination, the Omicron variant and the science behind Covid-19 infections dominated the discussion at a webinar organised on Monday (Feb 21) by the National University of Singapore's (NUS) Yong Loo Lin School of Medicine.

During the two-hour session - titled The New Normal: A Moving Target? - speakers also addressed topics such as virus mutations and the lessons to be learnt from the past two years.

These are the answers to some questions asked.

Q: Is there any difference between patients who have died of the Omicron variant and those who died of the Delta variant?

A: Yes, there is.

Dr Jyoti Somani, a senior consultant at the National University Hospital's infectious diseases division, said people with Delta infections tend to decline quickly.

They could go abruptly from "looking okay" to requiring supplemental oxygen, even though they had received timely medical treatment.

In contrast, people with the Omicron variant - even those who require oxygen for a time - manage to recover well.

Those who succumb tend to be frail or elderly, with other medical conditions, Dr Somani added.

"Just like if they had influenza or pneumonia, they may just succumb because they are frail, with underlying conditions."

Q: Some people continue to report lingering symptoms from Covid-19, months after being infected. Does vaccination help protect me from long Covid-19?

A: Yes, there is scientific evidence that vaccination can help reduce symptoms of long Covid-19, said Associate Professor David Lye, director of the National Centre for Infectious Diseases' infectious disease research and training office.

Long Covid-19 sufferers often complain of symptoms such as fatigue, muscle pain and breathing difficulties, and even depressive symptoms.

Having said that, it is unclear if some of these issues - such as those linked to depression - can be directly linked to Covid-19, the experts said.

This is because Covid-19 patients are being followed-up closely after recovery, making it easier for doctors to pick up on such problems.

Q: There are some indications that the BA.2 Omicron sub-variant, which has been detected in Singapore, can cause more severe disease. Should we be worried about this?

A: Laboratory studies from Japan found that hamsters infected with this sub-variant became sicker. There are also concerns that vaccines are less effective against this sub-variant.

But real-world experience from countries such as Denmark - where the BA.2 strain is now dominant - has not shown that people became more severely ill, Dr Somani said.

"I think there is concern, but we haven't seen it happen clinically yet," she added.

"These organisms are smart and they figure out ways around our protections, whether it's antibiotics or vaccines - so we still have a lot of work to do."

Q: Do we need new formulations of Covid-19 vaccines to deal with every new variant that emerges?

A: There is a good chance that pre-existing vaccines will have a cross-protective effect against new variants of the virus, said Associate Professor Paul MacAry, from NUS Medicine's microbiology and immunology department.

For instance, Omicron is very different from the variants the world has seen so far - yet, some degree of cross-protection exists, he said.

In fact, if people had to choose only one vaccine to use - as some resource-strapped countries might have to do - studies using mice have shown that the original formulation is likely to be best, said Professor Wang Linfa from Duke-NUS Medical School's emerging infectious diseases programme.

While the "ancestral vaccine" may be less effective against new variants, it still provides some degree of protection against such strains", he added.

"Now, if you go to the other extreme and give the mice the Omicron vaccine, they only have neutralising antibodies against Omicron - and zero against the other strains."