hide
Free keywords:
-
Abstract:
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.
Strategies that maintain low case numbers, instead of high ones, reduce infections and
deaths by factors of eleven and five, respectively. In general, policies with low case numbers
significantly benefit from vaccination, as the overall reduction in susceptibility will further
diminish viral spread. Keeping case numbers low is the safest long-term strategy because it
considerably reduces mortality and morbidity and offers better preparedness against emerging
escape or more contagious virus variants while still allowing for higher contact numbers
(freedom) with progressing vaccinations.
