  Vaccination against COVID-19 with the recently approved mRNA vaccines
BNT162b2 (BioNTech/Pfizer) and mRNA-1273 (Moderna) is currently underway in a
large number of countries. However, high incidence rates and rapidly spreading
SARS-CoV-2 variants are concerning. In combination with acute supply deficits
in Europe in early 2021, the question arises of whether stretching the vaccine,
for instance by delaying the second dose, can make a significant contribution
to preventing deaths, despite associated risks such as lower vaccine efficacy,
the potential emergence of escape mutants, enhancement, waning immunity,
reduced social acceptance of off-label vaccination, and liability shifts. A
quantitative epidemiological assessment of risks and benefits of non-standard
vaccination protocols remains elusive. To clarify the situation and to provide
a quantitative epidemiological foundation we develop a stochastic
epidemiological model that integrates specific vaccine rollout protocols into a
risk-group structured infectious disease dynamical model. Using the situation
and conditions in Germany as a reference system, we show that delaying the
second vaccine dose is expected to prevent deaths in the four to five digit
range, should the incidence resurge. We show that this considerable public
health benefit relies on the fact that both mRNA vaccines provide substantial
protection against severe COVID-19 and death beginning 12 to 14 days after the
first dose. The benefits of protocol change are attenuated should vaccine
compliance decrease substantially. To quantify the impact of protocol change on
vaccination adherence we performed a large-scale online survey. We find that,
in Germany, changing vaccination protocols may lead to small reductions in
vaccination intention. In sum, we therefore expect the benefits of a strategy
change to remain substantial and stable.
