S1182_SPI-M-O_Summary_of_modelling_of_easing_roadmap_step_2_restrictions.pdf
1of 23SPI-M-O: Summary of further modelling ofeasing restrictions–Roadmap Step 2Date: 31stMarch 2021Summary1.R in England is estimated to be between 0.8 and 1.0, higher than that estimated before schools reopened (between 0.6 to 0.8). As yet, the full effect of schools has not been fully reflected in these estimates nor has theimpactof easing restrictions from 29thMarch.2.The modelling presented here does not account for waning immunity nor the future emergence of immune-or vaccine-escapevariants.TheB.1.351 strain of SARS-CoV-2 is of particular concern for the UK,given the known reduced protection against mild tomoderate diseasefrom some vaccines. 3.There is considerable uncertainty about the level of control that can be achieved at each step of the Roadmap, and therefore the subsequent trajectory of hospital admissions and deaths. It remains criticalto evaluate the effect of each step before taking the next.4.While more data have accrued on real-world vaccine effectiveness and coverage, modelling results remain highly dependent on assumptions about unknown factorsincluding the rate of transmission at each stepas a result of behaviour changes; the extent to which baseline measures continue to reduce transmission once restrictions are lifted; the impact of seasonal changes in transmission; and future vaccine rollout speed.High vaccine coverage (90% in under 50-year olds) is assumedhere. Uncertainty increases when looking further into the future.5.Any resurgence in hospital admissions and deaths following Step 2 of the Roadmap aloneis highly unlikely to put unsustainable pressure on the NHS. 6.It is highly likely that there will be a further resurgence in hospitalisations and deathsafter the later steps of the Roadmap. The scale, shape, and timing of any resurgence remain highly uncertain;in most scenarios modelled,any peakis smaller than the wave seen in January 2021, however, scenarios with little transmission reduction after Step 4 orwith pessimistic but plausible vaccine efficacy assumptionscan result in resurgences in hospitalisations of asimilar scale to January2021.7.Maintaining baseline measures to reduce transmission once restrictions are lifted is almost certain to save many lives and minimise the threat to hospital capacity.8.Even accounting for some seasonal variation in transmission, thepeak could occur in either summer or late summer/autumn. It is possible that seasonality could delay or flatten the resurgence but is highly unlikely to prevent it altogether.
