IT is the “unresolved question” of the past four months: why did Scotland experience a dramatic surge in Covid cases after restrictions ended, while England did not - or at least, not to the same extent.

The puzzle, which has stumped public health experts and virus scientists alike, was flagged up this week in minutes from the Scottish Government’s Covid-19 Advisory Group.

The minutes, from a meeting held on October 14, note that Scotland and England “have been in tandem for most of the pandemic but not since around the time of the Euros”, which ended on July 11.

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They continue: “Infections in Scotland peaked, then declined without intervention and are now plateauing.

“There is an unresolved question as to why England did not peak to the same extent. It may be because things are so delicate that small movements have produced big changes.”

The also note that high levels of vaccination and high levels of infectiousness - as per the Delta strain - is “new territory”.

READ MORE: Scottish Government Covid advisors 'optimistic' about run up to Christmas

To understand why experts are perplexed, however, it is worth remembering just how dire some of the modelling for England was in the run up to its ‘Freedom Day’ on July 19, the date when nightclubs reopened, social distancing ended, and mandatory facemasks and work-from-home diktats were scrapped.

In the weeks before, cases were climbing rapidly and reached 50,000 on July 16.

Modellers forecast that Freedom Day would quickly propel England to 100,000 cases a day with hospitalisations potentially exceeding the winter Alpha wave.

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HeraldScotland: Hospital admissions in England have remained fairly high, but flat, in comparison to Scotland where admissions surged in SeptemberHospital admissions in England have remained fairly high, but flat, in comparison to Scotland where admissions surged in September

Instead, confirmed infections fell rapidly to around 21,000 by the end of July and have hovered ever since in a range of around 20,000-40,000 per day.

Hospital admissions have also remained steady at 560-860 per day, a quarter of the January peak.

In contrast, Scotland - which delayed its Freedom Day equivalent until August 9 and maintained masks and home working - saw cases rocket nearly five-fold in less than four weeks, reaching more than 6,400 by the beginning of September.

Peak hospitalisations, at 163 per day, were nudging levels seen at the height of wave one.

And while infections have largely plateaued in Scotland since the beginning of October, the two nations’ case rates are closer together than any other parts of the UK despite their respective governments' very different approaches to the pandemic: 373 per 100,000 in Scotland, and 433 per 100,000 in England.

HeraldScotland: Source: Public Health EnglandSource: Public Health England

Mask critics have pointed to the experience in Scotland - and Western Europe - compared to England as evidence that they are a useless mitigation.

But John Burn-Murdoch, a visiting senior fellow at London School of Economics (LSE) Data Science, whose work on Covid statistics is widely acclaimed, described the focus on masks in October as “overly simplistic, politicised and at times flat-out wrong”.

By mid to late-September in Scotland - where masks were required in shops, schools, public transport, and hospitality - weekly Covid case rates in the over-60s, hospitalisations per 100,000 and deaths per million were roughly twice as high in Scotland as England.

 

But, crucially, once masks were set aside, behaviours were almost identical in both nations in terms of public transport use and socialising in large gatherings or crowded spaces.

As Burn-Murdoch stressed, this is not proof that masks do not reduce incidence - they do, by around 10% - but that the benefit may be outweighed by other factors which more strongly encourage transmission.

“Just because masks are the most visible thing and the most easy for identifying ‘bad people’ to make ourselves feel a little better, they’re not the only factor or even the most important,” he said.

READ MORE: Vaccine passports will not be extended to pubs, cinemas and restaurants - for now

David Male, a professor of biology at the Open University who specialises in immunology, vaccines and variants, said the most likely answer is that Scotland coincided its ‘Beyond Zero’ phase with schools returning; in England, pupils went back six weeks after Freedom Day.

“I do think that quite probably the coincidence of those two things is responsible for that spike,” said Male.

“Because if you take out that spike at the end of the summer in Scotland, what’s happening across the United Kingdom is pretty similar in all four nations.”

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He added that while masks have little impact on exponential growth, they become more important once cases are flat.

“If you’ve got an epidemic that’s really taking off like it is in Austria, it needs more than mask wearing to get a hold of it.

"But if you’ve got something like what we have in the UK, measures like mask wearing can make the difference between the R value being above one and being below one, which makes a difference between the epidemic spreading or dying out.

“A small change in the rate of transmission now could, in six weeks’ time, make a big difference to the incidence.”

Another theory is that Scotland paid the price for having had a lower prevalence of the virus compared to England earlier in the pandemic.

READ MORE: Why the new Omicron variant has scientists scared 

Professor Rowland Kao, chair of veterinary epidemiology and data science at Edinburgh University, believes this could have been key.

He said: “In an ironic way - if you did better before you have less immunity now. Immunity obviously declines, but a fair bit sticks around.

“Given that, broadly speaking, Scotland has done better over the course of the pandemic it means that the proportion of individuals exposed to the disease is lower, and that means you’ve got less population immunity.”

It is certainly true that by the end of July, a higher percentage of adults in England than Scotland were testing positive for Covid antibodies - but the gap was just 1.5%: 92.6% compared to 91.1%.

In some age groups though the difference was wider: for example,roughly eight in 10 over-80s in Scotland had antibodies against nine in 10 in England.

HeraldScotland: Rowland KaoRowland Kao

It is difficult to say whether this was enough to swing the epidemic, but there is a growing consensus that the UK’s earlier and consistently higher exposure to Delta compared to Europe is now paying off - coupled with earlier booster rollouts.

Whether or not that was necessarily the best move for the NHS overall is less clear, however.

“It’s exactly the same argument as there was about herd immunity a year and a half ago, “said Kao.

“One of the things that we don’t know the answers to yet is whether that sort of continuous stream of people into the health service has been a net benefit or a net detriment, because that will obviously have a knock on effect for other procedures not being done.”

Professor Adam Kleczkowski, mathematical biology at Strathclyde University, admits to being “puzzled” by Covid trends in England since summer.

“The best explanation on what is going on in England at the moment is that it has reached something like ‘endemicity’, i.e. a state when the population immunity (vaccinated and post-infection) is so high that the reproductive number is close to one, even with (almost) complete relaxation.

“What we see now is, firstly, the pandemic ‘burning through’ the remaining susceptibles (non-vaccinated, children) and, secondly, infecting those whom vaccine waning made susceptible again.”

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HeraldScotland: Daily reported cases up to November 24, by age group, Scotland (black) vs England (blue) - courtesy of Professor Adam KleczkowskiDaily reported cases up to November 24, by age group, Scotland (black) vs England (blue) - courtesy of Professor Adam Kleczkowski

Comparing the countries’ infections by age group, though, it is clear that both experienced post-summer surges in the 0-14 and 15-19 age groups coinciding with schools returning.

While in Scotland this “propagated through other age groups”, England “has so far avoided the spread to 20 and above”.

Kleczkowski believes that higher levels of post-infection immunity in England compared to Scotland could have made the difference, enabling it to “vaccinate enough to spread out the outbreak” by the time schools returned.

READ MORE: Why the Delta variant has left herd immunity from vaccines alone mathematically impossible

However, he notes that when the countries are compared by Covid prevalence - the percentage of the population infected at any one time - surveillance indicates that England has been consistently higher recently.

"The main difference between Scotland and England in recent months is the big peak of cases at the beginning of the school year," said Kleczkowski.

"Except for this mid-August to mid-September peak, England has a higher percentage of cases than Scotland throughout the Autumn."

As for the weeks ahead, the new B.1.1.529 variant may well be a game-changer, necessitating much tougher measures than would ever be required with Delta should begin spreading in the UK and Europe.

Meanwhile, European regulators have just approved the Pfizer vaccine for five to 11-year-olds, a decision England's chief medical officer Chris Whitty insists remains far off for the UK.

So will England's policy of boosters and "letting rip" continue to outperform Western Europe - or should Scotland emulate continental precautions such as vaccine passports just in case?

"It is a very interesting topic, but it is too early to say," said Kleczkowski.

"The answer would depend on what happens over the next few weeks - will cases in England follow the current [European] trend, while Western Europe suppresses the peak?

"Or, would the Western Europe peak be so massive as to make it look like a basket case, and England just trots slowly, 'flattening the curve', but with a massive death toll?"