Germany’s fourth COVID-19 wave was mainly driven by the unvaccinated

Abstract

Background While the majority of the German population was fully vaccinated at the time (about 65%), COVID-19 incidence started growing exponentially in October 2021 with about 41% of recorded new cases aged twelve or above being symptomatic breakthrough infections, presumably also contributing to the dynamics. So far, it remained elusive how significant this contribution was and whether targeted non-pharmaceutical interventions (NPIs) may have stopped the amplification of the crisis. Methods We develop and introduce a contribution matrix approach based on the next-generation matrix of a population-structured compartmental infectious disease model to derive contributions of respective inter- and intragroup infection pathways of unvaccinated and vaccinated subpopulations to the effective reproduction number and new infections, considering empirical data of vaccine efficacies against infection and transmission. Results Here we show that about 61%–76% of all new infections were caused by unvaccinated individuals and only 24%–39% were caused by the vaccinated. Furthermore, 32%–51% of new infections were likely caused by unvaccinated infecting other unvaccinated. Decreasing the transmissibility of the unvaccinated by, e. g. targeted NPIs, causes a steeper decrease in the effective reproduction number than decreasing the transmissibility of vaccinated individuals, potentially leading to temporary epidemic control. Reducing contacts between vaccinated and unvaccinated individuals serves to decrease in a similar manner as increasing vaccine uptake. Conclusions A minority of the German population—the unvaccinated—is assumed to have caused the majority of new infections in the fall of 2021 in Germany. Our results highlight the importance of combined measures, such as vaccination campaigns and targeted contact reductions to achieve temporary epidemic control.

Nationwide population-based infection- and vaccine-induced SARS-CoV-2 seroprevalence in Germany at the end of 2021

“…Importantly, our data highlight how the higher prevalence of infection and of hybrid immunity detected in the eastern region is not sufficient to counterbalance the low prevalence of two vaccine doses when it comes to achieving a basic immunization. This corresponds to findings of a modelling study demonstrating how a minority of the German population, the unvaccinated, were the primary driver of the rise in new infections in the fall of 2021 30 .…”

“…Importantly, our data highlight how the higher prevalence of infection and of hybrid immunity detected in the eastern region is not sufficient to counterbalance the low prevalence of two vaccine doses when it comes to achieving a basic immunization. This corresponds to findings of a modelling study demonstrating how a minority of the German population, the unvaccinated, were the primary driver of the rise in new infections in the fall of 2021 30 One of the major strengths of our study is the use of a nationwide, population-based sample covering all the 400 districts in Germany, drawn from a long-running dynamic cohort that allows for sophisticated weighting and thus higher generalizability to the general population. Although some selection bias may be present, in general our study population shows good comparability with national surveillance data (see Supplement 6).…”

Study of the Deep Processes of COVID-19 in Russia: Finding Ways to Identify Preventive Measures

“…Research on the dynamics of COVID-19 in Germany also confirms the importance of vaccination: unvaccinated individuals were involved in 8–9 out of 10 new infections [ 32 ]. The study in Italy and Israel also found a positive impact of the vaccination campaign on the dynamics of the COVID-19 pandemic [ 33 , 34 ].…”

Ethics of Nudging in the COVID-19 Crisis and the Necessary Return to the Principles of Shared Decision Making: A Critical Review

“…With regard to the COSMO study under consideration, the question arises, to what extent the authors attempt to scientifically substantiate their recommendations. Coercive measures against the unvaccinated were apparently intended to be underpinned by a model calculation that involved the study authors, which accused the unvaccinated of having mainly caused the current COVID-19 crisis [ 204 ]. These claims were shown to be scientifically unfounded [ 205 , 206 ].…”

“…These claims were shown to be scientifically unfounded [ 205 , 206 ]. The complex modeling assumes unrealistic vaccine effectiveness, and claims an unrealistic faster recovery of vaccinated individuals after infection, which represents vaccine failure for them [ 204 ]. It was further argued that vaccine status identification (VSI) is associated with societal polarization and that mandatory regulations to get vaccinated could help to increase social cohesion as vaccination status will then become a less important part of one's self-concept [ 207 ].…”