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Lockdown could cut virus spread rate in half: Danish health agency

Denmark's SSI health agency has estimated that the tough lockdown measures the country has put in place could cut the rate the coronavirus pandemic spreads in the country by as much as half.

Published: 24 March 2020 14:07 CET

Lockdown could cut virus spread rate in half: Danish health agency

SSI believes the reproduction rate could fall by as much as 50 percent as a result of the lockdown measures. Photo: SSI

SSI (Statens Serum Institut), which is responsible for combatting infectious diseases in Denmark, said in its evaluation that it now believed that the virus's reproduction rate in Denmark before lockdown measures were put in place had been 2.1.

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This means that each person who caught the disease infected on average 2.1 more people over the course of their illness. The agency said it had developed this estimate by analysing of the rise in daily confirmed cases from 33 a day on March 13 to 83 cases a day on March 18, before the lockdown measures were put in place.

“If the current measures in society continue beyond March 30, the number of reproductions, that is, the number of people to whom each infection carries the infection, could be reduced by 30% to 50%,” the institute estimated.

It said it was basing its mathematical models on data from Italy, where the transmission rate had been higher at 2.6.

But the agency warned that achieving such a reduction would also require keeping public awareness and adherence to social distancing measures high throughout the spring.

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FACT CHECK: Did Sweden have lower pandemic mortality than Denmark and Norway?

At one point in May 2020, Sweden had the highest Covid-19 death rate in the world, spurring newspapers like the New York Times and Time Magazine to present the country as a cautionary tale, a warning of how much more Covid-19 could ravage populations if strict enough measures were not applied.

“Per million people, Sweden has suffered 40 percent more deaths than the United States, 12 times more than Norway, seven times more than Finland and six times more than Denmark,” the New York Times reported in July 2020.

An article in Time in October 2020 declared Sweden’s Covid response “a disaster”, citing figures from Johns Hopkins University ranking Sweden’s per capita death rate as the 12th highest in the world.

So there was undisguised glee among lockdown sceptics when Svenska Dagbladet published its data last week showing that in the pandemic years 2020, 2021 and 2022 Sweden’s excess mortality was the lowest, not only in the European Union, but of all the Nordic countries, beating even global Covid-19 success stories, such as Norway, Denmark and Finland.

Versions of the graph or links to the story were tweeted out by international anti-lockdown figures such as Bjørn Lomborg, a Danish sceptic of climate action, and Fraser Nelson, editor of Britain’s Spectator Magazine, while in Sweden columnists like Dagens Nyheter’s Alex Schulman and Svenska Dagbladet’s opinion editor Peter Wennblad showed that Anders Tegnell, the state epidemiologist who led Sweden’s strategy had been “right all along”.

Excess mortality — the number of people who die in a year compared to the number expected to die based on previous years — is seen by some statisticians as a better measure for comparing countries’ Covid-19 responses, as it is less vulnerable to differences in how Covid-19 deaths are reported.

But are these figures legitimate, where do they come from, and do they show what they purport to show?

Here are the numbers used by SvD in its chart:

Where do the numbers come from?

Örjan Hemström, a statistician specialising in births and deaths at Sweden’s state statistics agency Statistics Sweden (SCB), put together the figures at the request of Svenska Dagbladet.

He told The Local that the numbers published in the newspaper came from him and had not been doctored in any way by the journalists.

He did, however, point out that he had produced an alternative set of figures for the Nordic countries, which the newspaper chose not to use, in which Sweden had exactly the same excess mortality as Denmark and Norway.

“I think they also could have published the computation I did for the Nordic countries of what was expected from the population predictions,” he said of the way SvD had used his numbers. “It takes into consideration trends in mortality by age and sex. The excess deaths were more similar for Denmark, Sweden, and Norway. Almost the same.”

Here are Hemström’s alternative numbers:

Another issue with the analysis is that the SvD graph compares deaths in the pandemic years to deaths over just three years, a mean of 2017-2019, and does not properly take into account Sweden’s longstanding declining mortality trend, or the gently rising mortality trend in some other countries where mortality is creeping upwards due to an ageing population, such as Finland.

“It’s very difficult to compare countries and the longer the pandemic goes on for the harder it is, because you need a proper baseline, and that baseline depends on what happened before,” Karin Modig, an epidemiologist at Sweden’s Karolinska Institute whose research focuses on ageing populations, told The Local.

“As soon as you compare between countries, it’s more difficult because countries have different trends of mortality, they have different age structures, and in the pandemic they might have had different seasonal variations.”

She described analyses such as Hemström’s as “quite crude”.

In an interview with SvD to accompany the graph, Tegnell also pushed back against giving the numbers too much weight.

“Mortality doesn’t tell the whole story about what effect a pandemic has had on different countries,” he said. “The excess mortality measure has its weaknesses and depends a lot on the demographic structures of countries, but anyway, when it comes to that measure, it looks like Sweden managed to do quite well.”

Do the numbers match those provided by other international experts and media?

Sweden’s excess mortality over the three years of the pandemic is certainly below average worldwide, but it is only in the SvD/SCB figures that it beats Norway and Denmark.

A ranking of excess mortality put together by Our World in Data for the same period as the SvD/SCB table estimates Sweden’s excess mortality between the start of 2020 and the end of 2022 at 5.62 percent, considerably more than the 4.4 percent SvD claims and above that of Norway on 5.08 percent and Denmark on 2.52 percent.

The Economist newspaper also put together an estimate, using their own method based on projected deaths.

Our World in Data uses the estimate produced by Ariel Karlinsky and Dmitry Kobak, who manage the World Mortality Dataset (WMD). To produce the estimate, they fit a regression model for each region using historical deaths data from 2015–2019, so a time period of five years rather than the three used by SCB.

What’s clear, is that, whatever method you use, Sweden is, along with the other Nordic countries, among the countries with the lowest excess mortality over the pandemic.

“Most methods seem to put Sweden and the other Nordic countries among the countries in Europe with the lowest cumulative excess deaths for 2020-2022,” said Preben Aavitsland, the Director for Surveillance and the Norwegian Institute of Public Health.

So if Sweden had similar excess mortality as the other Nordics over the period, does that mean it had a similar Covid-19 death rate?

Not at all. Sweden’s per capita death rate from Covid-19 over the period covered by the SvD/SCB figures, at 2,249 per million people, is more than double Norway’s 959 per million, 60 percent more than the 1,409 per million who died in Denmark, and more than 50 percent more than the 1,612 per million who died in Finland.

While Sweden’s death rate is still far ahead of those of its Nordic neighbours, it is now much closer to theirs than it was at the end of 2020.

“The most striking difference between Sweden and the other Nordic countries is that only Sweden had large excess mortality in 2020 and the winter of 2020-21,” Aavitsland explained. “In 2022, the field levelled out as the other countries also had excess mortality when most of the population was infected by the omicron variant after all measures had been lifted.”

So why, if the Covid-19 death rates are still so different, are the excess mortality rates so similar?

This largely reflects the fact that many of those who died in Sweden in the first year of the pandemic were elderly people in care homes who would have died anyway by the end of 2022.

About 90 percent of Covid-19 deaths were in people above 70, Aavitsland pointed out, adding that this is the same age group where you find around 80 percent of all deaths, regardless of cause, in a Scandinavian country.

“My interpretation is that in the first year of the pandemic, say March 2020 – February 2021, Sweden had several thousand excess deaths among the elderly, including nursing home residents,” he said. “Most of this was caused by Covid-19. In the other [Nordic] countries, more people like these survived, but they died in 2022. The other countries managed to delay some deaths, but now, three years after, we end up at around the same place.”

So does that mean Sweden’s state epidemiologist Anders Tegnell was right all along?

It depends on how you view the shortened lives of the close to ten thousand elderly people who caught Covid-19 and died in Sweden in the first wave because Sweden did not follow the example of Denmark, Norway, and Finland and bring in a short three-week lockdown in March and April 2020.

Tegnell himself probably said it best in the SvD interview.

“You’ve got to remember that a lot of people died in the pandemic, which is of course terrible in many ways, not least for their many loved ones who were affected, so you need to be a bit humble when presented with these kinds of figures.”

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