Can a mild flu season really explain Sweden’s high coronavirus mortality?

Can a mild flu season really explain Sweden's high coronavirus mortality?
An intensive care unit at Södertälje hospital south of Stockholm during the peak of the crisis. Photo: Staffan Löwstedt / SvD / TT
A mild flu season could be one of the reasons for Sweden's comparatively high Covid-19 death rate, Swedish state epidemiologist Anders Tegnell, the figurehead of the country's coronavirus response has said, but his Norwegian counterpart says the assertions don't stack up.

“When many people die of the flu in the winter, fewer die in heatwaves the following summer. In this case, it was Covid-19 that caused many to die,” Tegnell told Dagens Nyheter.

“What has now been seen is that the countries that have had a fairly low mortality for influenza in the last two, three years, such as Sweden, have a very high excess mortality in Covid-19. Those which had a high flu mortality rate, such as Norway, during the last two winters, have fairly low Covid mortality. The same trend has been seen in several countries. This may not be the whole explanation but part of it.”

Chart showing total deaths from Covid-19. Adjusted per capita, Sweden has seen 576 deaths per million inhabitants, compared to 110 in Denmark, 61 in Finland, and 50 in Norway.

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When The Local asked the Public Health Agency for details about the report in question, a press spokesperson for the agency said it was a paper from three economics researchers, which has not been peer-reviewed and suggests 15 possible factors for Sweden's much higher death toll than neighbouring countries.

The report did not discount that the lack of lockdown may have been a factor, but said it believed the most significant other factor was a high number of vulnerable elderly, partly due to a mild flu season the year before. Its authors note: “From the onset of Covid, we have been highly skeptical of lockdown measures.”

In the section of the report concerning mortality from flu, the authors cite Twitter users @EffectsFacts, @FatEmperor and @HaraldofW.

The Local also asked the Public Health Agency if comparisons of the flu mortality rate in recent years were available in official statistics or a peer-reviewed study, but had not received a response by the time of publication.

When contacted by The Local, Tegnell's Norwegian counterpart Frode Forland questioned the claim that Norway had suffered more severe flu seasons than Sweden in recent years.

“There was a rather mild season last year in both Norway and in Sweden,” Frode Forland told The Local.

“We have had a relationship between the spread in society and the number of deaths in vulnerable groups,” he said. “It's been proportional, the death rate compared to the number of people infected in society.” 

Sweden does have a higher coronavirus case fatality rate (the ratio between confirmed deaths and confirmed cases) than its Nordic neighbours, although this is not necessarily due to a higher proportion of frail people, since Sweden has tested far fewer people throughout the epidemic than Norway, Denmark and Finland, for a long time only offering tests to people requiring hospital or medical care.

Asked on Swedish television if he stood by the claims that a mild flu season was the reason for Sweden's high mortality rate, Tegnell said on Friday: “[The factors behind Sweden's high mortality are] comparable to, for example, the Netherlands, which seems to have a pandemic that is very similar to ours, which does not resemble the Norwegian development. There were also major shutdowns [in the Netherlands] so I really think we should wait before we do major evaluations and comparisons with different countries. If this article was wrong, it should be discussed with the article authors.”

In Sweden, 7,928 people were infected with influenza in the 2019-2020 season, compared with 13,758 the season before and 20,686 in the 2017-2018 season, Public Health Agency statistics show. The number of deaths within 30 days of a flu diagnosis was 178 in 2019-2020, compared to 451 the season before and 1,012 in the 2017-2018 season.

The Swedish agency has previously pointed to the lower level of spread of flu in 2020 as evidence that its coronavirus measures, such as recommending people wash hands and stay at home while symptomatic, were effective in preventing spread of infections.

Denmark experienced the mildest flu season in several years in 2019-2020, although the country's figures are not directly comparable with Sweden's due to slight differences in reporting. A total of 97 people in Denmark died within 30 days of being diagnosed with influenza, but the country also provides estimates of total influenza mortality, which was 119 in 2019-2020, compared to 790 in the 2018-2019 season, 2,822 people in the 2017-2018 season and 751 people in the 2016-17 season.

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  1. Please, It is important to show the graphic in deaths/habitants. This can shows the correct comparative. Thank you.

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