Extended scenarios for England for lifting non-pharmaceutical interventions (NPIs) as set out by the Cabinet Office were explored. Detailed/specific policy changes cannot be modelled. Instead, the increase in transmissibility from successive easing of NPIs was translated as per Table 1, accounting for the considerable uncertainty in transmissibility associated with each step in our estimates of R. Vaccine roll out schedules (Table 3) were pre-specified. Current levels of transmissibility are based on our latest estimates for England at Reff (including immunity) =0.75 (translating to Rexcl_immunity =1.10 with an estimated 32% of the population currently protected via prior infection- and/or vaccine-induced immunity). Table 4 shows vaccine efficacy assumptions against severe disease, symptomatic disease and infection after each dose (Pfizer and AstraZeneca). Four sensitivity analyses were performed, using 1) slower vaccine roll out; 2) pessimistic vaccine efficacy; 3) lower adherence to NPI measures retained after full lifting (i.e. return to a higher baseline transmissibility) and 4) including seasonality in SARS-CoV-2 transmissibility. We assumed an age-dependent vaccine uptake (Table 5). Summary
1. Due to eligibility and vaccine hesitancy, vaccination alone will not be sufficient to keep the epidemic under control. NPIs must be lifted slowly and cautiously to minimise the number of deaths and prevent high hospital occupancy, with some baseline NPIs remaining in place (and adhered to) throughout 2021 and beyond.
2. It is critical to achieve and maintain high vaccine uptake and roll out before easing NPIs.
3. Assuming optimistic vaccine efficacy, even if 3.2M vaccine doses/week are given up to 12 July (3.9M thereafter), only 46% of the population will be protected against disease (due to vaccination or recovery from infection) at the date of full NPI lifting in scenario 1 (26 April 2021), 60% in scenario 4 (2 August), and 65% in scenario 5a (16 July) (Fig 1A).
4. Relaxing too quickly (scenario 1) will result in peak hospital occupancy considerably higher than the current wave and substantial additional deaths (Fig 1E-F). This holds regardless of vaccine efficacy, roll out, adherence to baseline NPIs, and impact of seasonality.
5. Scenario 4 will still result in a substantial additional number of deaths (58,200, 95%CrI 31,000 - 95,300) by June 2022 in our main analysis.
6. Scenarios 5a and 5b where NPIs return to Tier-1 like restrictions on 27th April and 11th May 2021, and are fully lifted on 16th July 2021, result in a smaller but prolonged wave of hospitalisations compared to the current wave, and lead to an additional 55,000 (95%CrI:33,200 - 81,200) and 54,800 (95%CrI: 32,600 - 82,900) deaths, respectively.
7. Our results are highly dependent on the assumed (optimistic) vaccine efficacy, uptake, and rollout speed. Due to the uncertainty surrounding these assumptions, it is critical to rapidly assess the true effectiveness of vaccination within the population as it may be lower than clinical efficacy reported in trial settings. Our results also assume no loss of infection- or vaccineinduced immunity on the time horizon of the analysis. Characterising the duration of vaccineimmunity will be critically important.
8. With a lower vaccine efficacy, all scenarios would lead to a third wave of hospitalisations larger than or comparable in magnitude to the current wave (Fig 3-A2).
9. A return to higher transmissibility levels after NPIs are lifted will also lead to a third wave of hospitalisations comparable in magnitude to the current wave (Fig 3-A1). Therefore, whilst the impact of Test Trace Isolate (TTI), mask wearing, hand hygiene, and COVID security on R is difficult to quantify, it will be vital to emphasise the importance of normalising and ensuring adherence to all measures even after “full lifting” is achieved.
10. Assessing the impact of each relaxation before committing to the next phase is critical. Impact of waning immunity and other VOC is particularly difficult to assess at present.