Time needed to find out how virulent Omicron is: Experts

Two weeks before useful data from UK, Norway and Denmark - where strain is dominant - is out

Two more weeks - that is when more will be known of the Omicron Covid-19 variant that has countries worldwide rushing to take precautionary measures, including tightening their borders.

Perhaps by then, countries will be able to make more science-based decisions on how to deal with this new variant that has sat the world on its ear.

Omicron, which surfaced in South Africa last month and was declared a variant of concern by the World Health Organisation the same month, is known to be far more transmissible than Delta, currently the dominant viral strain fuelling the Covid-19 pandemic.

But that is about all that is really known of this variant at this point: That Omicron has a host of mutations, including several that are known to boost transmissibility of the virus, and it spreads more easily than Delta.

Associate Professor Hsu Li Yang, an infectious diseases expert at the National University of Singapore (NUS) Saw Swee Hock School of Public Health, said that given the lag time between infection and severe illness and deaths, another two weeks should see useful data emerging from the United Kingdom, Norway and Denmark.

Omicron is fast becoming the dominant strain in these countries, with Norway predicting that it will push infections to above 90,000 a day by early next month, from about 6,000 a day now.

On Thursday, new infections in the UK topped 88,000, the highest daily number since the start of the pandemic.

Prof Hsu said: "We will know even more about the virulence of the Omicron variant over the next two weeks, in view of the escalating case counts in Europe and the UK. Then we can be more confident about current projections about its impact on Singapore."

He said that while early data from South Africa indicates a milder illness, the question is whether that is due to people already having some form of immunity through prior infection or vaccination, or if Omicron is truly less virulent.

Also, many of those infected were younger, for whom Covid-19 is generally a milder illness.

Associate Professor Alex Cook, vice-dean of research at the NUS Saw Swee Hock School of Public Health, said: "The key unknown in my mind is the severity profile in people who are not previously infected but are vaccinated (or have had booster shots)."

This would be the majority of people in Singapore, as 87 per cent of the population have been fully vaccinated, and 31 per cent have had their booster jabs.

Like Prof Hsu, he said data from South Africa may not relate well to Singapore, given that large swathes of its population had been infected in early waves of the pandemic.

"I'm watching the UK closely as it is a better proxy for Singapore, though still imperfect as their vaccine rates are lower and past infections greater than ours," said Prof Cook.

Associate Professor David Allen, an infectious diseases expert at the National University Hospital, said that if the disease does prove to be milder, it will be less of a burden on the healthcare system.

A possible concern, he added, is that "it is too early to know whether Omicron is associated with more, less, or the same risk of long Covid-19; and the potential impact on quality of life, economic productivity, need for additional non-hospital healthcare services that may entail".

But even if it does produce milder illness with no increase in incidence of long Covid-19, where people sometimes remain breathless and tire easily for months after they have recovered, there are other implications.

Health Minister Ong Ye Kung said earlier this week: "Even if Omicron infections are indeed milder, it can still cause us big problems.

"If the risk of hospitalisation, requiring oxygen supplementation or ICU (intensive care unit) is, let's say, half that of Delta, but the Omicron variant can spread to twice as many people, the two factors cancel out, which means our healthcare system will face the same pressure as when we had the Delta wave.

"And if Omicron spreads faster to unvaccinated seniors, the problem is actually bigger."

About one in four of the 160,000 people above the age of 15 who remain unvaccinated are seniors for whom the risk of severe illness is higher.

Prof Allen agreed, saying: "The surge in cases will be in the unvaccinated. There will be cases in the vaccinated but skewed even farther on the asymptomatic-to-mild end of the spectrum."

So the key questions are how virulent this mutation is, and the protection afforded by vaccines against infection and severe illness should people be exposed to Omicron.

Prof Hsu said: "Given that Singapore has a highly vaccinated population, I am cautiously optimistic that we will see an overall reduced impact of Omicron here compared to the Delta variant.

"If we could ramp up the vaccination of children prior to widespread community transmission of Omicron, that will be even better."

Should Omicron prove to cause a much milder illness than Delta with very few deaths, then it might be a good thing should it become the dominant strain, as a mild infection could boost a person's immunity to future infections.

Today, while Omicron can be found in almost 80 countries, it accounts for less than 3 per cent of Covid-19 cases around the world, with the exception of Africa where about 90 per cent of cases are caused by this variant.

If the vast majority of people infected are asymptomatic or only mildly ill, with only a tiny fraction of 1 per cent - as against the 1.3 per cent today - needing hospital care, then Covid-19 would truly have become an endemic disease we can learn to live with.

But if a milder infection still means 1 per cent or more of those infected will require hospital care, including oxygen supplementation or intensive care, then current precautions will have to continue.

If the infection is half as deadly but spreads four times as fast, it could result in double the number of severely ill people.

If that should be the case, then current measures might need to be enhanced, since the more rapid spread of Omicron could lead to many more people needing the limited number of hospital beds.

Against this is the high level of protection against symptomatic illness caused by Omicron in people who have received booster shots.

As a result, countries facing an Omicron wave, such as the UK, are rushing out booster shots in their population.

The European Medicines Agency has declared that boosters can be safely and effectively given three months after a person has been fully vaccinated, "should such a short interval be desirable from a public health perspective".

In Singapore, 31 per cent of the population have received their booster shots, with another more than two million vaccine doses expected to be given over the next two months.

Vaccination for children aged five to 11 will also start before the end of the year.

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A version of this article appeared in the print edition of The Straits Times on December 18, 2021, with the headline Time needed to find out how virulent Omicron is: Experts. Subscribe