Just 7.3% of Stockholm’s inhabitants had developed Covid-19 antibodies by the end of April, according to a study, raising concerns that the country’s light-touch approach to the coronavirus may not be helping it build up broad immunity.

The research by Sweden’s public health agency comes as Finland warned it would be risky to welcome Swedish tourists after figures suggested the country’s death rate per capita was the highest in Europe over the seven days to 19 May.

Sweden’s state epidemiologist, Anders Tegnell, said the antibodies figure was “a bit lower than we’d thought”, but added that it reflected the situation some weeks ago and he believed that by now “a little more than 20%” of the capital’s population had probably contracted the virus.