Politico

Sweden catches first glimpse of herd immunity


STOCKHOLM — Sweden’s maverick response to the coronavirus has thrown up a new controversy: immunity levels.

This week, officials at the Swedish Public Health Agency, which devised the country’s no-lockdown strategy, claimed the rate of coronavirus immunity in Stockholm could be as high as 40 percent and is already playing a big role in pushing back the disease.

“We are clearly at levels which are very significant,” lead epidemiologist Anders Tegnell told reporters at a news briefing on Tuesday. “The reduction we are now seeing speaks strongly in favor of a very large immunity in the population.”

It appeared to be a rare piece of good news in a country that has seen a stubbornly high infection rate and inevitably raised hopes that so-called herd immunity — where an immune group protects a still-susceptible group from disease — could be near. Previous estimates have suggested herd immunity rates when it comes to coronavirus could be around 45-50 percent of the population.

However, critics were quick to challenge the Public Health Agency’s statements.

Twenty-five Swedish doctors and scientists published an open letter attacking the government’s approach to tackling the virus and claiming immunity rates were well below those mentioned by the agency, and possibly as low as 10 percent.

One of the authors of the letter, virologist Lena Einhorn, acknowledged that cases of COVID-19 — and the death rate from the disease — are falling in Sweden, but she disputed the idea that immunity is a big factor.

She cited better hygiene routines within elderly care homes and the fact that many Swedes are social distancing at summer homes as more important factors.

“The reasons are manifold, but it is unlikely that herd immunity is playing any major role,” she told POLITICO.

She said a weakness in the Public Health Agency’s 40 percent immunity estimate is that less than half of it was based on positive tests for antibodies, which are regarded as a clear sign that a person has had coronavirus and recovered. The remaining half of the agency’s estimate relates to less well-understood parts of the immune system, which are believed to result in a patient being immune, but not testing positive for antibodies to coronavirus.

Einhorn said this reflects a “completely unproven assumption.”

The debate in Sweden illustrates how much is still unknown as the pandemic continues to sweep the globe. Along with how best to measure immunity and herd immunity, key questions also remain about how long immunity lasts and in some quarters, whether it exists at all.

Swedish epidemiologist Tegnell said his agency is working on the assumption that those who have recovered from the virus are immune and that the immunity lasts for at least six months.

Speaking to POLITICO after his press briefing Tuesday, Tegnell said the uneven spread of the disease makes measuring immunity levels difficult.

“We are now collecting a number of different samples and trying to put them together,” he said.

The flare-up in Sweden over immunity rates is the most recent twist in a dispute which began when Sweden chose to go its own way in the early days of the pandemic.

Back then, while Nordic neighbors like Norway and Denmark were quickly shutting schools and businesses to stop the spread of coronavirus, Sweden kept society largely open, saying it was looking for a slow and manageable spread of the virus.

A raft of critics, some of whom are the same experts who penned this week’s critical letter, said the government was leading Sweden to disaster.

They said not locking down early was a mistake, as was not making face masks mandatory and not carrying out more extensive contact tracing and quarantining.

The number of deaths per million in Sweden, at 561, is below the worst-hit countries in Europe, including the U.K. and Spain, but has now spiked to nearly 12 times that of neighboring Norway and around 10 times that of Finland.

Swedes are still banned from traveling to some European nations, including Nordic neighbors Norway, Denmark and Finland.

Yet Tegnell is standing by his light-touch approach, saying that while the exact role of immunity is hard to pinpoint exactly, the recent fall in the number of cases of coronavirus is good news and to some extent validates his country’s approach.

“It shows that also the Swedish strategy can establish a very rapid fall in cases the same way as lockdowns have done,” he said.

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