Modelling the impact of lockdown easing measures on cumulative COVID-19 cases and deaths in England

Background As countries begin to ease the lockdown measures instituted to control the COVID-19 pandemic, there is a risk of a resurgence of the pandemic, and early reports of this are already emerging from some countries. Unlike many other countries, the UK started easing lockdown in England when levels of community transmission were still high, and this could have a major impact on case numbers and deaths. However thus far, the likely impacts of easing restrictions at this point in the pandemic have not been quantified. Using a Bayesian model, we assessed the potential impacts of successive lockdown easing measures in England, focussing on scenarios where the reproductive number ( R ) remains ≤1 in line with the UK government’s stated aim. Methods We developed a Bayesian model to infer incident cases and R in England, from incident death data from the Office of National Statistics. We then used this to forecast excess cases and deaths in multiple plausible scenarios in which R increases at one or more time points, compared to a baseline scenario where R remains unchanged by the easing of lockdown. Findings The model inferred an R of 0.752 on the 13 th May when England first started easing lockdown. In the most conservative scenario where R increases to 0.80 as lockdown was eased further on 1 st June and then remained constant, the model predicts an excess 257 (95% 108-492) deaths and 26,447 (95% CI 11,105-50,549) cumulative cases over 90 days. In the scenario with maximal increases in R (but staying ≤1) with successive easing of lockdown, the model predicts 3,174 (95% 1,334-6,060) excess cumulative deaths and 421,310 (95% 177,012-804,811) excess cases. Results When levels of transmission are high, even small changes in R with easing of lockdown can have significant impacts on expected cases and deaths, even if R remains ≤1. This will have a major impact on population health, tracing systems and health care services in England.. Following an elimination strategy rather than one of maintenance of R below 1 would substantially mitigate the impact of the COVID-19 epidemic within England. This study provides urgently needed information for developing public health policy for the next stages of the pandemic.