A new Swedish coronavirus antibody study shows the herd immunity strategy isn't working

• A new study by Sweden's public health agency found that just 7% of people in Stockholm had caught the coronavirus by the end of April.
• Swedish forecasters had previously predicted up to half the population would catch the virus by May.
• Experts say at least 60% of people need to catch the virus before any protective immunity can be achieved.
• "It's surprising [the forecasts] are so wrong," Professor Tom Britton, who helped devise the public health agency's model said.

A new study suggests that only a small percentage of people in Sweden's capital Stockholm have developed coronavirus antibodies, casting doubt over whether the country's avoidance of strict lockdown measures is helping to provide any significant immunity in the population.

The research, based on 1,100 tests across Sweden and carried out by the country's public health agency, found that just 7.3% of people had developed antibodies which could provide immunity, Reuters reported.

However, experts say populations can only achieve so-called 'herd immunity' to a virus when around 60% of the population have caught it.

Professor Tom Britton, who helped develop the agency's forecasting model, admitted that their calculations may have been "quite wrong."

"It means either the calculations made by the agency and myself are quite wrong, which is possible, but if that's the case it's surprising they are so wrong," he told the Swedish newspaper Dagens Nyheter, according to the Guardian.

"Or more people have been infected than developed antibodies."

Britton had previously suggested that half the country would have become infected by the end of April.

The new study casts doubt on suggestions that Sweden's strategy would provide them with greater protection to the virus in the long-term.

The findings also come as Sweden this week overtook the United Kingdom, Italy, and others to become the worst affected country in the world in terms of coronavirus deaths per capita.

Unlike most other European countries, Sweden's government has decided against strict, wholesale lockdown measures in response to the coronavirus pandemic.

Instead, the country has allowed businesses and its hospital industry to remain largely open, while students still attend school.

It is also taking a relaxed approach to testing compared to most other countries. The Swedish government has a modest target of carrying out 100,000 a week, Reuters reported, and is focusing mainly on health care workers and people in hospital.

The Swedish government has not explicitly said that it is aiming for herd immunity but has said that it wishes to slow the spread of the virus in order to ensure that the capacity of its health service is not breached.

Herd immunity 'is a long way off, if we ever reach it'

The new findings will come as a challenge to proponents of the herd immunity strategy.

Bjorn Olsen, Professor of Infectious Medicine at the Uppsala University, told Reuters: "I think herd immunity is a long way off, if we ever reach it."

However, Anders Tegnell, the country's head epidemiologist, told reporters that the findings reflected the situation in April, and that he believed around 20% — or one in five — people in Stockholm had now caught the coronavirus.

The Swedish government insists that its strategy will pay-off in the long run.

Earlier this month, Tegnell, who leads its public health agency, said that while countries who imposed strict lockdowns would likely suffer large second waves later in the year, Sweden's would be smaller in comparison.

"In the autumn there will be a second wave. Sweden will have a high level of immunity and the number of cases will probably be quite low," Tegnell told The Financial Times.

Comparing Sweden to its neighbour, Tengell said: "But Finland will have a very low level of immunity.

"Will Finland have to go into a complete lockdown again?"

Sweden's public health agency, which Tegnell heads, predicted that 40% of people in Stockholm will have caught the COVID-19 virus by the end of this month, The Times of London reported.