A new study finds Stockholm had the same coronavirus infection rate as London, casting yet more doubt on the herd immunity theory

• A study comparing coronavirus exposure in London and Stockholm casts more doubt over herd immunity.
• It found that the two capital cities had the same infection rate — 17% — earlier in the summer.
• This is despite the UK and Sweden taking very different approaches to the coronavirus pandemic.
• Unlike the UK and most other countries, Sweden opted against strict lockdown measures.
• This decision was taken partly in the belief that herd immunity was achievable.
• Sweden's state epidemiologist predicted that 40% of Stockholm would have antibodies by May.

Stockholm and London both had the same coronavirus infection rates earlier in the summer, according to a new study, casting yet more doubt on the herd immunity theory.

Unlike most European countries, Sweden did not implement strict lockdown measures in response to the outbreak of the COVID-19 virus. Instead, it allowed shops, bars, and restaurants to remain largely open and students to attend school.

The United Kingdom like most other countries imposed a nationwide lockdown, with Boris Johnson's government closing offices, schools, and the hospitality industry, and restricting social contact between individuals.

Sweden's state epidemiologist Anders Tegnell, who is widely credited as the architect of the country's contentious response to the pandemic, justified Sweden's response by saying countries that imposed strict lockdowns would most likely suffer large second waves later in the year, whereas Sweden's would be smaller.

In April, he predicted that by May 40% of people in the Sweden's capital Stockholm would have developed coronavirus antibodies.

However, a study carried out by University College London academics and published in the Journal of the Royal Society of Medicine, estimated that the level of infection in Stockholm in April was actually around 17% — the same level as in London, according to analysis of tests carried out in England's capital in April and May.

The study poses a further challenge to herd immunity — the theory that a population will become immune to the coronavirus when at least 60% of people catch it.

Sweden opted against strict lockdown measures partly in the belief that this level of infection was achievable in the foreseeable future.

Dr Simon Clarke, a professor in Cellular Microbiology at the University of Reading, told The Daily Mail newspaper: "Natural herd immunity, generated by letting COVID-19 sweep through a population, may have been an appealing notion to some because of the lack of a lockdown or curbs on people's freedoms, but it was nothing more than an idea which lacked supporting data.

"The Swedish experience of attempting to achieve this, compared to other Nordic countries responses, resulted in much higher numbers of infections and deaths per capita, in addition to a prolonged outbreak," he continued.

"These findings should prove a salutary warning, that appealing concepts and theories require supporting data when people's lives are at stake and should not be used to fit pre-conceived narratives."

5,770 people in Sweden have died after testing positive for coronavirus as of Wednesday morning, giving it one of Europe's highest death tolls per capita.

The figure is far higher than in neighboring countries with similar political systems and social customs. Its per-capita death figure is more than five times Denmark's, more than 11 times Norway's, and almost 10 times Finland's.

The UK 'nearly trod the same path' as Sweden

There is currently insufficient evidence that coronavirus antibodies provide immunity to the virus. People who catch a virus usually develop antibodies, which can be measured by tests.

It is not clear, howver, whether having antibodies offers total — or even partial — immunity to COVID-19, or how long such an effect may last.

A study by Kings College London published last month found that while 60% of people with the coronavirus had "potent" antibodies, just 17% had the same level of potency three months later. The potency of the antibodies fell by as much as 23 times over the three months and in some cases antibodies were undetectable at the end of that period of time.

The findings put "another nail in the coffin of the dangerous concept of herd immunity," Jonathan Heeney, a professor of virology at the University of Cambridge, said at the time.

Prime Minister Johnson's UK government has denied initially trying to pursue a strategy of herd immunity before it was warned that it would lead to the deaths of hundreds of thousands of people.

An Italian health minister in June said Johnson revealed his plan to pursue herd immunity in a phone call with Italian Prime Minister Giuseppe Conte on March 13, a little more than a week before the UK entered a countrywide lockdown.

On the same day, Patrick Vallance, the chief scientific adviser to the UK government, said he believed the UK would be able to achieve herd immunity.

The scientists behind the research, UCL's David Goldsmith and Eric Orlowski, said: "Lest this strategy seem like just the traditional risky Swedish exceptionalism, we in the UK would do well to remember we nearly trod the same path.

"Right now, despite 'strict (but tardy) lockdown' in the UK, and the more measured Swedish response, both countries have high seven-day averaged Sars-CoV-2 death rates when compared to other Scandinavian and European countries."