Playing Hardball in Government and Politics

Lockdowns had a dramatic impact on the spread of coronavirus in Europe with strict controls on people’s movements preventing an estimated 3.1m deaths by the beginning of May, with 470,000 deaths averted in the UK alone, researchers say.

Outbreak modellers at Imperial College London said that lockdown slashed the average number of people that contagious individuals infected by 81% and lowered the reproduction number, R, of the epidemic below 1 in all countries they observed.

When R is less than 1 the epidemic is in decline because on average, each infected person transmits the infection to less than one other. As countries ease out of their lockdown, scientists are watching R closely: if it rises and remains above 1, the epidemic will grow exponentially.

The Imperial team pooled data on Covid-19 deaths from 11 European countries including the UK, Italy, France, Spain and Germany, and worked backwards to calculate the extent of transmission several weeks earlier, to account for the time lag between infections and deaths. Lockdown at the end of March reduced the reproductive number of the UK epidemic from 3.8 to 0.63, they calculate.

The model shows that by 4 May between 12 million and 15 million people had become infected, but some nations were hit far harder than others. According to the model Belgium had the largest number of cases per capita with 8% of the population infected, compared with only 0.46% of Norwegians and 0.85% of Germans. Some 5.1% of the UK population was infected, according to a report published in Nature.

“Our model estimates that we are very far away from herd immunity,” said Axel Grandy, a professor of statistics at Imperial and co-author on the study. Herd immunity is achieved when enough people are immune to a virus that outbreaks die out naturally. In the case of Covid-19, scientists believe upwards of 70% of the population would need to be resistant for herd immunity to kick in.

“It tells us we need to be very careful and not to release too much in one go because then you have no control,” Prof Gandy said. “We need to tread very carefully and do things slowly, so we can backtrack should they not work.”