Fig. 6.

Systematic investigation of the interplay between vaccination strategies and social interaction scenarios, to estimate the time by which herd immunity might be reached. Luxembourg (A), Austria (B) and Sweden (C). Panels A, B and C: indicative dates at which herd immunity might be reached, depending on combinations of social interaction parameter and number of fully vaccinated people/day. The black grid indicates the combinations of social interaction and vaccination speed that would not allow to achieve herd immunity before 2022. In all panels, vertical lines indicate the three alternative vaccination strategies described in the main text. Depending on measures and population behaviour, estimated levels of social interaction since the beginning of the pandemic have been mostly between $0.15$ and $0.5$ (i.e. $15\%$ to $50\%$ of social interactions w.r.t. before the pandemic). Assumptions of vaccination, like 100% efficacy, are summarised and discussed in Section 2.1 and Section 4. The red dashed line represents an estimate of the number of fully vaccinated people per day for each country, averaged over time from 27 December , 2020 to 15 July , 2021.