How Fast Must Vaccination Campaigns Proceed in Order to Beat Rising Covid-19 Infection Numbers?

Facing a third Covid-19 outbreak in the spring of 2021 a central question for European policymakers is at what point a vaccination campaign has acquired sufficient speed to overcome the increase in infections, so as to justify lifting NPIs at least partially. The authors of this study derive an expression for a critical threshold that is shaped by three factors: First, the mortality risk from a Covid-19 infection increases exponentially with age. Second, the sizes of age cohorts decrease linearly at the top of the population pyramid. And third, vaccination proceeds at an increasing speed. The study finds that it is easier for countries with a comparatively young population and fast vaccination programs to reach this critical threshold than for countries with an older population and slower vaccination programs. An important conclusion of the research is, that slow vaccination hurts twice: The number of vaccinated people increases only at a slow rate. But it also means that vaccination programs’ ability to control aggressive new Covid-19 strains is strongly reduced.