Fig. 4. Projections of epidemic dynamics under different control measures.

We compare four alternative scenarios for nonpharmaceutical interventions from 1 January 2021: (i) mobility returning to levels observed during relatively moderate restrictions in early October 2020; (ii) mobility as observed during the second lockdown in England in November 2020, then gradually returning to October 2020 levels from 1 March to 1 April 2021, with schools open; (iii) as (ii), but with schools closed until 15 February 2021; (iv) as (iii), but with a lockdown of greater stringency as observed in March 2020 (fig. S20). (A) Without vaccination. (B) With 200,000 people vaccinated per week. (C) With 2 million people vaccinated per week. We assume that vaccination confers 95% vaccine efficacy against disease and 60% vaccine efficacy against infection, and that vaccination starts on 1 January 2021 with vaccine protection starting immediately upon receipt. This is intended to approximate the fact that vaccination started in early December, with full protection occurring after a time lag and potentially after a second dose. Vaccines are given first to people aged 70+ until 85% coverage is reached in this age group, then to people aged 60+ until 85% coverage is reached in this age group, continuing into younger age groups in 10-year decrements. Resurgences starting in March 2021 are due to the relaxation of nonpharmaceutical interventions, including reopening schools (fig. S20). Median and 95% credible intervals are shown. The dashed lines in rows 2 and 3 show peak hospitalizations and deaths from the first COVID-19 wave in England (April 2020).