Sweden, unlike its Nordic neighbors Denmark and Norway – and virtually every other country in the western world – has resisted extensive lockdown restrictions to stem the coronavirus outbreak. Instead, it's largely kept society, including schools and restaurants open, and relied on voluntary social-distancing measures that appeal to the public's sense of self-restraint. Polls show the strategy is broadly supported by most Swedes. 

Scientists in Sweden and abroad have accused the country of dangerously pursuing "herd immunity" – the idea that by building a broad base of recovered infections in society the disease will eventually stop spreading because a majority of people will not be susceptible. "Herd immunity" is usually achieved by vaccination and takes place when a large enough percentage of the population are immune.  

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Anders Tegnell, chief epidemiologist at Sweden’s Public Health Agency – the nation's top infectious disease official and architect of Sweden's coronavirus response –denied that "herd immunity" formed the central thrust of Sweden's containment plan, in an interview with USA TODAY. Yet he also said the country may be starting to see the impact of "herd immunity."

This is a lightly edited transcript of USA TODAY's interview with Tegnell.

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What's the latest from Sweden?

Tegnell: We are doing two major investigations. We may have those results this week or a bit later in May. We know from modeling and some data we have already – these data are a little uncertain – that we probably had a transmission peak in Stockholm a couple of weeks ago, which means that we are probably hitting the peak of infections right about now. We think that up to 25% of people in Stockholm have been exposed to coronavirus and are possibly immune. A recent survey from one of our hospitals in Stockholm found that 27% of staff there are immune. We think that most of those are immune from transmission in society, not the workplace. We could reach herd immunity in Stockholm within a matter of weeks. 

(Editor's note: The World Health Organization has warned that individuals who have had COVID-19 are not necessarily immune, by the presence of antibodies, from getting the virus again. They might be, but the scientific work hasn't reached the stage where that has been conclusively proved. Tegnell said that, at the population level, if antibodies can't be viewed as an indication of immunity then this undermines the whole rationale for developing a vaccine. "If you can't get population immunity how can we then think a vaccine will protect us?" he said. The precise percentage required for "herd immunity" changes based on the disease. Britain briefly entertained a "herd immunity" strategy before altering course amid a rapidly rising death toll. Britain's chief scientific officer concluded that a figure of 60% might be needed for COVID-19. It could be months before a fuller picture emerges of who remains vulnerable to coronavirus.)

What is Sweden's COVID-19 strategy?

Tegnell: We are trying to keep transmission rates at a level that the Stockholm health system can sustain. So far that has worked out. The health system is stressed. They are working very hard. But they have delivered health care to everybody, including those without COVID-19. That is our goal. We are not calculating herd immunity in this. With various measures, we are just trying to keep the transmission rate as low as possible. The amount of cases has been stable for the last two-to-three weeks. We believe herd immunity will of course help us in the long run, and we are discussing that, but it's not like we are actively trying to achieve it as has been made out (by the press and some scientists). If we wanted to achieve herd immunity we would have done nothing and let coronavirus run rampant through society. We are trying to keep the transmission rate as low as we can. We have taken reasonable measures without really hurting health care or schools. We are going for a sustainable strategy; something we can keep on doing for months. Coronavirus is not something that is just going to go away. Any country that believes it can keep it out (by closing borders, shuttering businesses, etc.) will most likely be proven wrong at some stage. We need to learn to live with this disease. 

What has voluntary social distancing meant for Sweden's economy?

Tegnell: You'll need to ask our economists. I know nothing about this. But at a glance it looks to me that Sweden's economy is doing a lot better than others'. Our strategy has been successful because health care is still working. That's the measure we look at.

(Editor's note: Sweden’s COVID-19 strategy may ultimately result in a smaller – albeit historically deep – economic contraction than the rest of Europe is now facing, according to a recent Bloomberg article, citing an HSBC Global Research economist. Surveys show that about half of Swedes are working from home, use of public transport is down by about 50% and economic activity has slowed. But shops, restaurants and hair salons remain open. Still, Sweden's Finance Minister Magdalena Andersson has warned that annual GDP could shrink by 10% and unemployment rise to 13.5%. Economic forecasts for the U.S. vary. Some economists believe GDP will suffer a double-digit decline in the second quarter. The Congressional Budget Office forecasts a whopping 28% annual decline for U.S. GDP, but this assumes four consecutive quarterly declines of 7%. Many economists predict the U.S. economy may rebound this summer. The March unemployment rate in the U.S. stood at 4.4%. White House economic adviser Kevin Hassett has forecast that the figure for April could soar to 16-17%.). 

Have Sweden's voluntary measures led to more deaths more quickly than if it had imposed a mandatory lockdown?

Tegnell: We don't really know yet. What the crisis has shown is that we need to do some serious thinking about nursing homes because they have been so open to transmission (more than a third of Sweden's COVID-19 fatalities have been reported in nursing homes) of the disease and we had such a hard time controlling it in that setting. However, this is only indirectly related to our strategy because the strategy was to protect those people and that part of it did not work out. This is perhaps not a surprise because there has always been a problem with running these homes safely in Sweden going back a long time. That's something we are taking advice on now and that we intend to do better on. 

(Editor's note: Sweden has a population of 10 million people, about twice as large as its nearest Scandinavian neighbors. As of April 28, the country's COVID-19 death toll reached 2,274, about five times higher than in Denmark and 11 times higher than in Norway, according to John Hopkins University's coronavirus tracker.)

What if your strategy fails? Plan B?

Tegnell: It's not just me running this. It's the entire agency and the government. We are all having continuous discussions about what we are doing and whether it's the right thing. So far everyone is reasonably OK with it, with the exception of the high proportion of deaths in nursing homes. But it's also accepted that this is to a great extent a separate problem. Crucially, the public is on our side. They are worried, about the economy, but not that the disease is spreading uncontrollably in Sweden. We have many reasons to think that we are doing the right thing. It's true that our death toll is higher compared to Denmark and Norway, but we have a lot of other things going for us. If you compare us to other countries in Europe who have severe lockdowns we are doing at least as good as them and in many cases better. Every country is wondering whether they are doing the right thing. What's happening now is that many countries are starting to come around to the Swedish way. They are opening schools, trying to find an exit strategy. It comes back to sustainability. We need to have measures in place that we can keep on doing over the longer term, not just for a few months or several weeks. 

What's your take on the US strategy?

Tegnell: I don't know it well enough but it still seems to me that the Americans let coronavirus go too far before any real strategy came into place. One of the real big problems in the beginning was the lack of testing. I'm also not really sure how well the U.S. health system can change as dramatically as we in Sweden have been able to, for example. We have almost double the intensive care capacity that we had a couple of weeks ago. Being centrally organized and steered (as part of a state-funded system) allows for greater flexibility in changing the health system. I'm not sure how well that can be done in the U.S. with all the private actors and insurance firms. It may make it more difficult to handle this kind of situation. 

(Editor's note: According to the most recent data available, published by the National Institutes of Health prior to the coronavirus outbreak, the U.S. had between 20-31 intensive care bed units per 100,000 people; Sweden had been between 6-9 per 100,000 people. After a slow start, U.S. testing has accelerated.)