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Despite never implementing a full-scale lockdown, Sweden has managed to flatten its curve, prompting its health leadership to claim victory -- but others question the cost of the strategy, as the country has a far higher death toll than its Scandinavian neighbors.

In late July, Sweden's was about 200, down from a peak of around 1,140 in mid-June. Its have been in the single digits for two weeks, well below its mid-April peak of 115 deaths in a single day.

However, on a per-capita basis, Sweden far outpaces its Scandinavian neighbors in COVID deaths, with 567 deaths per million people compared with Denmark's 106 deaths per million, Finland's 59 deaths per million, and Norway's 47 deaths per million. The Swedish figure is closer to Italy's 581 deaths per million.

While the positive trends have led Anders Tegnell, PhD, chief epidemiologist at the Swedish Public Health Agency and architect of Sweden's coronavirus strategy, to state that the "," others have criticized the approach, including two dozen Swedish academics who published a .

"In Sweden, the strategy has led to death, grief, and suffering," they wrote. "On top of that, there are no indications that the Swedish economy has fared better than in many other countries. At the moment, we have set an example for the rest of the world on how not to deal with a deadly infectious disease."

The Swedish Public Health Agency has not openly stated that herd immunity was its goal, though many suspect this was the intention. Tegnell told reporters last week he thought the recent trends indicated that immunity was now widespread in the country. But with rates of antibody positivity around 10%, that seems impossible. (Officials at the agency did not respond to 麻豆传媒's request for comment.)

So how has Sweden managed to get its outbreak under control?

Behavior Change

While Sweden didn't officially lock down, many in the country have described a locked-down "feeling" that has eased in the summer months.

At the start of the outbreak, only high schools and universities closed; daycare and elementary schools have been open. Businesses have also remained open, but typically at reduced hours, and restaurants have functioned at reduced capacity.

Swedes have been asked to keep their distance in public, refrain from non-essential travel, and work from home when possible. Gatherings of more than 50 people are also banned. People age 70 and over are advised to stay away from others as much as possible.

Masks were never required and aren't commonly worn.

This response hasn't changed over time, through the June surge and into today's decline, so there's no definitive explanation for the flattening, though, and experts have several theories.

"Swedes in general have changed their behavior to a great extent during the pandemic and the practice of social distancing as well as physical distancing in public places and at work has been widespread," said Maria Furberg, MD, PhD, an infectious diseases expert at Umea University Hospital in northeastern Sweden.

"During the months of March to early June, all shops were practically empty, people stopped dining with friends, and families stopped seeing even their closest relatives," Furberg told 麻豆传媒. "A lock-down could not have been more effective. Handwashing, excessive use of hand sanitizers, and staying home at the first sign of a cold became the new normal very quickly."

Mozhu Ding, PhD, an epidemiologist at the famed Karolinska Institute, said the decline is "likely to be a combination of measures taken by individuals, businesses and a widespread information campaign launched by the government."

"Even without a strict lockdown order, many businesses allowed employees to work from home, and universities are offering distance courses to the students," Ding told 麻豆传媒. "Individuals are also taking personal hygiene more seriously, as items like hand sanitizers and single-use gloves are often sold out in pharmacies and grocery stores."

Immunity

Experts told 麻豆传媒 there weren't clear data to prove Tegnell's assertion of widespread immunity in Sweden.

Furberg said there is likely "some sort of unspecific immunity that protects parts of the population from contracting COVID-19" but it's not necessarily secondary to SARS-CoV-2 exposure.

For instance, recently found that about 30% of people with mild or asymptomatic COVID showed T-cell-mediated immunity to the virus, even though they tested negative for antibodies.

"This figure is [more than] twice as high as the previous antibody tests, meaning that the public immunity to COVID-19 is probably much higher than what antibody studies have suggested," Ding told 麻豆传媒. "This is of course very good news from a public health perspective, as it shows that people with negative antibody test results could still be immune to the virus at a cellular level."

Indeed, T-cell immunity is coming into focus as a potentially important factor in COVID infection. A paper found that among 37 healthy people who had no history of either the first or current SARS virus, more than half had T cells that recognized one or more of the SARS-CoV-2 proteins.

Another 36 people who had mild-to-severe COVID-19 were all found to have T-cell responses to several SARS-CoV-2 proteins, and another 23 people who had SARS-CoV-1 (the virus responsible for the SARS outbreak in 2003) all had lasting memory T cells -- even 17 years later -- that also recognized parts of SARS-CoV-2.

It could be that T cell immunity is the result of a previous infection with common cold coronaviruses, but this hasn't yet been established; nor is it certain that T cell immunity is driving Sweden's decline in COVID cases.

Path Forward

Summertime is another factor that may account for the decline, which began around late June -- not directly because of the weather, but social factors related to it.

Swedes are "outdoors more, and students are not at school," said Anne Spurkland, MD, a professor of immunology at the University of Oslo in Norway.

Also, "perhaps Sweden has finally gotten better control over the disastrous spread of the virus in nursing homes which to some extent can explain their relatively high death rates," Spurkland told 麻豆传媒. About half of Sweden's 5,730 deaths occurred among those in elder care homes.

Norway is still requiring that Swedes quarantine for 10 days when coming into Norway, and Denmark has not fully reopened its borders to its neighbor yet either.

That doesn't bode well for the Swedish economy. If the goal of avoiding a lockdown was to spare economic woe, its success has been limited.

, "international tourism and trade are decimated. ... Sweden's National Institute of Economic Research predicts Sweden's GDP will fall 5.4% in 2020, after predicting a 1% rise [in] December 2019. It also expects unemployment to rise around three percentage points, to 9.6%, between the end of 2019 and the end of 2021."

Spurkland said it's still "too early yet to conclude whether the Swedish approach was the wisest over all," as it remains to be seen whether Norway and other countries that did lock down will avoid a second wave of infections in the fall.

Yet she cautions that choosing to take on a higher case load may have health consequences far beyond the immediate infection.

"What we have learned these months is that COVID-19 is not only about death, it is also about ill health," Spurkland said. "Quite a number of people going through the infection have long-term symptoms, that may be stopping them from resuming their daily life. We do not know yet how large a proportion of those who get the virus will fall into this category, but it is certainly a concern."

"So when deciding on taking a herd immunity approach to handle a totally new virus we do not know anything about," she said, "the Swedish government has also unknowingly put the general population at risk for much long-term ill-health caused by the virus."

Furberg doesn't see it that way: "I am very proud of the way Swedes have adapted to the restrictions and regulations and I believe the Public Health Agency of Sweden has picked a good-enough strategy for our country."

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