‘The standard thing to do when you’re faced with really quite deep uncertainties is to be cautious. The precautionary principle is rational.’

That was the message this week from Professor Sir David Spiegelhalter, arguably the UK’s foremost statistician whose position at Cambridge University is geared to improving the public’s understanding of risk.

Exactly what constitutes over- and under-reaction to the Omicron variant at this stage is difficult to gauge because there is still very little we know about it for certain.

But wearing face coverings, working from home as much as possible, limiting “unnecessary” social interactions (as recommended by UK Health Security Agency chief Dr Jenny Harries), and taking a lateral flow test before mixing with others at parties, pubs or restaurants are hardly draconian interventions.

Scrapping office Christmas parties altogether – or nativity plays, senior citizens’ festive lunches, and the rest – is a harder call.

READ MORE: Total number of confirmed Omicron cases in Scotland rises to 29 

On the one hand they are potential super-spreading events; on the other, it remains unclear how widespread Omicron is in the community or whether it is significantly more dangerous (in terms of transmissibility, virulence, or vaccine escape) than Delta, which is continuing to notch up over 2,500 cases a day in Scotland.

So, one week on, how much do we know about this new ‘variant of concern’?

There is little doubt that South Africa is experiencing an explosive Covid surge.

It has gone from reporting an average of around 200 to 300 infections a day two weeks ago to more than 8,500 in a single 24 hour period on Wednesday of this week.

According to South Africa’s National Institute for Communicable Diseases (NICD), 74 per cent of all the virus genomes it sequenced in November were Omicron, suggesting that Delta is being rapidly displaced.

 

 

It also appears that Omicron is spreading faster in South Africa’s population that any of the previous variants – from the original Wuhan strain to either Beta or Delta.

But South Africa’s demographics make it difficult to predict how it will behave here: less than 6% of South Africa’s population is over 65 compared to 19% in Scotland.

At the same time, only 24% of South Africa’s total population has been fully vaccinated, mostly with Pfizer, and almost no one has had a booster (those who have are healthcare workers who received a second shot of the Johnson & Johnson single-dose vaccine).

In Scotland, 72% of the total population is fully vaccinated and one in three people have already had a booster.

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Much higher levels of immunity combined with mitigations such as masks, home-working, and lateral flow tests which reduce the virus’ opportunities to be passed on should, at least, curb the rise of Omicron.

But if does turn out to be significantly more transmissible than Delta – which had an estimated R number of six – then vaccines will still be less effective at stopping it spreading between people and infecting even the fully vaccinated, regardless of whether its mutations make it more resistant to existing immunity or not.

We already saw that happen when Delta replaced Alpha as the dominant variant.

READ MORE: Masks, home working, and longer restrictions - so why did cases spike in Scotland but not England?

It would also be the case that more people would end up in hospital than would have done with Delta, simply based on the maths that the virus would reach more people overall.

At the moment, data from England tracking the prevalence of Covid cases with the ‘S-gene dropout’ – a marker for Omicron – indicates that these rose from 0.1% to 0.3% of infections between November 24 and November 28.

In Scotland, there are tentative signs that the recent fall in infections stalled around November 27.

The Herald: Covid cases stopped falling - and may have begun to increase - on November 27Covid cases stopped falling - and may have begun to increase - on November 27

This could herald the arrival of a new, fast-spreading variant; but it could also simply be a return to the October plateau.

The question of whether Omicron will reduce the effectiveness of vaccines will be clearer by Christmas, but it depends on a combination of real-world observations and laboratory analysis.

Scientists are currently growing samples of Omicron or genetically engineering viral particles with the Omicron’s highly mutated spike protein.

These can then be tested against the sera – the antibody-rich fluid in blood – collected from vaccinated or recovered patients.

This will enable researchers to determine how effectively existing Covid antibodies – generated either by our current vaccines or exposure to previous strains of the virus – can kill off, or “neutralise”, the Omicron pathogen.

The Herald: A woman receives a dose of a Covid-19 vaccine in Soweto, South Africa, yesterday. The country has only 24 per cent of its population fully vaccinated

This process is expected to take around one to two weeks, but epidemiologists will also be tracking changes in hospitalisation patterns that may give us an early warning signal.

There are reports from Israel of people triple-vaccinated with Pfizer passing Omicron on to other triple vaccinated individuals, but what we really want to know is how well people are still protected against serious disease.

Harvard epidemiologist William Hanage said this week that he would “fall off my chair if it turned out that the vaccines’ efficacy against serious illness was seriously affected”.

In South Africa, hospitalisations with Omicron are rising, but appear to be rising in line with the previous Beta and Delta waves, rather than mirroring the almost vertical spike in cases.

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In a best case scenario, this could tell us that Omicron causes less severe illness, but it could also simply reflect that there is higher natural- and vaccine-acquired immunity now than in previous waves, or that it is mostly younger people infected.

Right now, in Scotland, unvaccinated people are being admitted to hospital at four times the rate of fully vaccinated people (18.26 versus 4.45 admissions per 100,000).

If Omicron caused vaccine protection against serious illness to erode, we would start to see that gap narrowing.

In a very highly vaccinated population like Scotland’s, this would happen quickly if Omicron suddenly became dominant.

Right now the picture is far from clear, however. Caution – not panic – makes sense.