Sweden's controversial decision to keep most schools, bars, salons and restaurants open during the COVID-19 crisis while the rest of Europe shut down around could end up taking a much higher toll on the country than expected.
A study carried out by Sweden's Public Health Agency found that despite the country's relaxed distancing measures, only 7.3% of people in Stockholm have developed the antibodies necessary to fight the disease, far below the 70-90% of the population needed to achieve herd immunity.
The study drew on some 1,100 tests from across the country, although only figures for Stockholm were released on Wednesday. Results from other regions would be released later, a Public Health Authority spokesperson said. However, Stockholm is by far Sweden's most densely populated city, with around 5,000 citizens per square kilometer, which makes it much more likely to be the first city to achieve herd immunity in the country.
Sweden's chief epidemiologist Anders Tegnell, who spearheaded the strategy, said the number was a "little lower" than expected "but not remarkably lower, maybe one or a couple of percent."
Meanwhile, Sweden's strategy for handling the coronavirus epidemic has led to Sweden having a significantly higher death rate than the surrounding Nordic countries, with very few measures in place to ensure a flattening of its curve.
Dr. Mike Ryan, executive director of the World Health Organization (WHO) Health Emergencies Program, said the concept of herd immunity was a "dangerous calculation."
The WHO has warned against pinning hopes on herd immunity. It said last week that global studies had found antibodies in only 1-10 percent of the population, results in line with recent findings in Spain and France.
According to figures collated by the Our World in Data website, Sweden had 6.08 deaths per million inhabitants per day on a rolling seven-day average between May 13 and May 20.
This is the highest in the world, above the UK, Belgium and the US, which have 5.57, 4.28 and 4.11 respectively.
On April 24, Tegnell told BBC radio that the authorities believed Stockholm had "an immunity level... somewhere between 15 and 20% of the population."
He said the strategy had "worked in some aspects ... because our health system has been able to cope. There has always been at least 20% of the intensive care beds empty and able to take care of Covid-19 patients."
Asked whether Sweden's approach will help it withstand a possible second wave, Tegnell said he believed it would.
"It will definitely affect the reproduction rate and slow down the spread," he said, but added that it wouldn't be enough to achieve "herd immunity."