  We propose a simple rule of thumb for countries which have embarked on a
vaccination campaign while still facing the need to keep non-pharmaceutical
interventions (NPI) in place because of the ongoing spread of SARS-CoV-2. If
the aim is to keep the death rate from increasing, NPIs can be loosened when it
is possible to vaccinate more than twice the growth rate of new cases. If the
aim is to keep the pressure on hospitals under control, the vaccination rate
has to be about four times higher. These simple rules can be derived from the
observation that the risk of death or a severe course requiring hospitalization
from a COVID-19 infection increases exponentially with age and that the sizes
of age cohorts decrease linearly at the top of the population pyramid.
Protecting the over 60-year-olds, which constitute approximately one-quarter of
the population in Europe (and most OECD countries), reduces the potential loss
of life by 95 percent.
