Sonabend R, Whittles LK, Imai N, et al. - For the stepwise lifting of non-pharmaceutical interventions (NPIs) in England, the timeline and conditions were set out by England's COVID-19 roadmap out of lockdown policy as vaccination roll-out continued, with step one initiating on March 8, 2021. In this mathematical modelling study, the roadmap has been assessed, the impact of the Delta (B.1.617.2) variant of SARS-CoV-2, and potential future epidemic trajectories have been described.

• The UK Government's four-step process to easing lockdown restrictions in England, UK, appeared successful in limiting the increased transmission due to lifting NPIs, with increasing population immunity through vaccination.

• The emergence of the delta variant, with an estimated transmission advantage of 76% over alpha, might have led to 3,900 peak daily hospital admissions under the central parameter scenario if there would have been full lifting of NPIs on June 21, 2021, as originally planned.

• Peak hospital admissions reduced by three fold to 1,400 per day due to delaying the lift until July 19, 2021.

• A substantial uncertainty is estimated in the epidemic trajectory, with particular sensitivity to the transmissibility of delta, level of mixing, and measures of vaccine effectiveness.

• Overall, a substantial mitigation of the risk of a large wave of COVID-19 hospital admissions resulting from lifting NPIs can be attained by carefully balancing the timing of NPI relaxation against vaccination coverage.

• However, even with high vaccination coverage, full lifting of NPIs might not be possible with the Delta variant without a third wave of hospital admissions and deaths.