Large-scale lockdowns and other non-pharmaceutical interventions in Europe have been successful in reducing the transmission levels of coronavirus, according to a modelling study from Imperial College London.

The study, published online in Nature used death data to infer changes in the course of the Covid-19 epidemic as a result of non-pharmaceutical interventions. They analysed data from 11 countries in Europe, including the UK, Spain, Italy, Germany and Belgium, up until 4 May 2020.

The team estimate that by that date between 12 and 15 million individuals in these countries had been infected with coronavirus (3.2% to 4% of the population, with large country-to-country fluctuations). By comparing the number of observed deaths against those predicted by their model in the absence of interventions, the authors suggest that approximately 3.1 million deaths have been averted due to non-pharmaceutical measures. 

They calculate that the reproduction number has dropped to below one as a result of the interventions, decreasing by an average of 82%, although the values vary from country to country.

The rate of transmission has declined from high levels

Dr Samir Bhatt, study author from the MRC Centre for Global Infectious Disease Analysis, Jameel Institute (J-IDEA), Imperial College London: “This data suggests that without any interventions, such as lockdown and school closures, there could have been many more deaths from Covid-19. The rate of transmission has declined from high levels to ones under control in all European countries we study. Our analysis also suggests far more infections in these European countries than previously estimated. Careful consideration should now be given to the continued measures that are needed to keep SARS-CoV-2 transmission under control.”

The use of pooled data and the short time separation between subsequent non-pharmaceutical interventions makes it difficult to determine the effect of individual sanctions on the suppression of the Covid-19 epidemic.

One limitation of the model is that it assumes that each measure had the same effect on all countries, whereas in reality, there was variation in how lockdown was implemented in different countries. However, the authors conclude that lockdown has a substantial effect in reducing the reproductive number below one and has helped to contain the spread of Covid-19 as of the beginning of May.