  Mass vaccination offers a promising exit strategy for the COVID-19 pandemic.
However, as vaccination progresses, demands to lift restrictions increase,
despite most of the population remaining susceptible. Using our age-stratified
SEIRD-ICU compartmental model and curated epidemiological and vaccination data,
we quantified the rate (relative to vaccination progress) at which countries
can lift non-pharmaceutical interventions without overwhelming their healthcare
systems. We analyzed scenarios ranging from immediately lifting restrictions
(accepting high mortality and morbidity) to reducing case numbers to a level
where test-trace-and-isolate (TTI) programs efficiently compensate for local
spreading events. In general, the age-dependent vaccination roll-out implies a
transient decrease of more than ten years in the average age of ICU patients
and deceased. The pace of vaccination determines the speed of lifting
restrictions; Taking the European Union (EU) as an example case, all considered
scenarios allow for steadily increasing contacts starting in May 2021 and
relaxing most restrictions by autumn 2021. Throughout summer 2021, only mild
contact restrictions will remain necessary. However, only high vaccine uptake
can prevent further severe waves. Across EU countries, seroprevalence impacts
the long-term success of vaccination campaigns more strongly than age
demographics. In addition, we highlight the need for preventive measures to
reduce contagion in school settings throughout the year 2021, where children
might be drivers of contagion because of them remaining susceptible...
