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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. Author summary: In this work, we quantify the rate at which non-pharmaceutical interventions can be lifted as COVID-19 vaccination campaigns progress. With the constraint of not exceeding ICU capacity, there exists only a relatively narrow range of plausible scenarios. We selected different scenarios ranging from the immediate release of restrictions to more conservative approaches aiming at low case numbers. In all considered scenarios, the increasing overall immunity (due to vaccination or post-infection) will allow for a steady increase in contacts. However, deaths and total cases (potentially leading to long covid) are only minimized when aiming for low case numbers, and restrictions are lifted at the pace of vaccination. These qualitative results are general. Taking EU countries as quantitative examples, we observe larger differences only in the long-term perspectives, mainly due to varying seroprevalence and vaccine uptake. Thus, the recommendation is to keep case numbers as low as possible to facilitate test-trace-and-isolate programs, reduce mortality and morbidity, and offer better preparedness against emerging variants, potentially escaping immune responses. Keeping moderate preventive measures in place (such as improved hygiene, use of face masks, and moderate contact reduction) is highly recommended will further facilitate control. [ABSTRACT FROM AUTHOR]

We present a simple but accurate algorithm to calculate the flow and shear rate profile of shear thinning fluids, as typically used in biofabrication applications, with an arbitrary viscosity-shear rate relationship in a cylindrical nozzle. By interpolating the viscosity with a set of power-law functions, we obtain a mathematically exact piecewise solution to the incompressible Navier-Stokes equation. The algorithm is validated with known solutions for a simplified Carreau-Yasuda fluid, full numerical simulations for a realistic chitosan hydrogel as well as experimental velocity profiles of alginate and chitosan solutions in a microfluidic channel. We implement the algorithm in an easy-to-use Python tool, included as Supplementary Material, to calculate the velocity and shear rate profile during the printing process, depending on the shear thinning behavior of the bioink and printing parameters such as pressure and nozzle size. We confirm that the shear stress varies in an exactly linear fashion, starting from zero at the nozzle center to the maximum shear stress at the wall, independent of the shear thinning properties of the bioink. Finally, we demonstrate how our method can be inverted to obtain rheological bioink parameters in-situ directly before or even during printing from experimentally measured flow rate versus pressure data. [ABSTRACT FROM AUTHOR]

Across Europe, the COVID-19 pandemic is causing excess deaths, placing a burden on societies and health systems and harming the economy. Overwhelming evidence shows that not only public health, but also society and the economy benefit greatly from reducing cases of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Supplementary Material Supplementary appendix Graph Panel A joint European strategy for the COVID-19 pandemic B 1 Achieve low case numbers b (i) Aim for a target of no more than ten new COVID-19 cases per million people per day. [Extracted from the article]

Call for a pan-European COVID-19 response must be comprehensive - Authors' reply. [Extracted from the article]

Competing Interests: VP was a member of the ExpertInnenrat of the German federal government on COVID and an advisor for other governmental and non-governmental entities. The remaining authors declare no competing interests.

In the summer of 2021, European governments removed most NPIs after experiencing prolonged second and third waves of the COVID-19 pandemic. Most countries failed to achieve immunization rates high enough to avoid resurgence of the virus. Public health strategies for autumn and winter 2021 have ranged from countries aiming at low incidence by re-introducing NPIs to accepting high incidence levels. However, such high incidence strategies almost certainly lead to the very consequences that they seek to avoid: restrictions that harm people and economies. At high incidence, the important pandemic containment measure 'test-trace-isolate-support' becomes inefficient. At that point, the spread of SARS-CoV-2 and its numerous harmful consequences can likely only be controlled through restrictions. We argue that all European countries need to pursue a low incidence strategy in a coordinated manner. Such an endeavour can only be successful if it is built on open communication and trust., Competing Interests: TC was supported by the EU Commission, grant agreement No 101016233 (PERISCOPE). SB was supported by Netzwerk Universitätsmedizin, project egePan (01KX2021). ACV's institution was supported by Ministry of Culture and Science of the German State of North Rhine-Westphalia. EGl was supported by the Luxembourg National Research Fund (FNR) with Public funding support with payments to the host institute as part of the COVID-19 Fast-Track grant research project CovScreen (COVID-19/20201/14715687). EGr has received payments for a manuscript on the history of pandemics. JK is employed by a project funded by the European Research Council, European Union's Horizon 2020 research and innovation programme (grant agreement no. 724460). CL received grants from the University of Oxford, National Centre for Smoking Cessation and Training, UK, Horizon 2020, EUROPEAN COMMISSION, and Pfizer Inc, royalties from Olvos Science, payment for expert testimony from Word Health Organization and European Commission, has a patent for Cretan Iama Olvos Science, and is on the advisory board for Pfizer Helas and Vianex SA. GNP received grants and royalties from Novartis, FNIH, Gilead Grants, managed through NIH, and is the chair of the Nemitsas Prize Award Committee. MPi was supported by Wellcome Trust [grant numbers: 209519/Z/17/Z; WT106612MA], MRC [grant number: MR/S035818/1], ESRC [grant numbers: ES/T014164/1; ES/S013873/1], and British Academy [EN160164]. ESz's lab receives funding for other projects from Merck Healthcare. ST's institution received grants due to his role as Co-investigator-PI in study under the European Union's Horizon 2020 research and innovation programme, Grant Agreement, No 883441, under the agreement and control of the Special Committee for Research Grants of the University of Athens, Athens, Greece. PWilmes’ institution received grants from the European Commission's Horizon 2020 programme including the European Research Council (CoG 863664), the Luxembourg National Research Fund, and the University of Luxembourg, and owns patents. PWilmes received honoraria for being on two PhD juries at the University of Copenhagen and for the Maud Menten lecture at the University of Western Ontario, and for membership of the scientific steering committee for a clinical trial by 4D Pharma plc. and he is Co-speaker of the Research Luxembourg COVID-19 Task Force. Vice-president of the Luxembourg Society for Microbiology. All these were unrelated to this article. All other authors declare no competing interests., (© 2021 The Authors.)

How will the coronavirus disease 2019 (COVID-19) pandemic develop in the coming months and years? Based on an expert survey, we examine key aspects that are likely to influence the COVID-19 pandemic in Europe. The challenges and developments will strongly depend on the progress of national and global vaccination programs, the emergence and spread of variants of concern (VOCs), and public responses to non-pharmaceutical interventions (NPIs). In the short term, many people remain unvaccinated, VOCs continue to emerge and spread, and mobility and population mixing are expected to increase. Therefore, lifting restrictions too much and too early risk another damaging wave. This challenge remains despite the reduced opportunities for transmission given vaccination progress and reduced indoor mixing in summer 2021. In autumn 2021, increased indoor activity might accelerate the spread again, whilst a necessary reintroduction of NPIs might be too slow. The incidence may strongly rise again, possibly filling intensive care units, if vaccination levels are not high enough. A moderate, adaptive level of NPIs will thus remain necessary. These epidemiological aspects combined with economic, social, and health-related consequences provide a more holistic perspective on the future of the COVID-19 pandemic., Competing Interests: ENI, VP, SB, and SBM were supported by the Max Planck Society. VP received honoraria for lectures and presentations on COVID-19 mitigation strategies. PB was supported by the Epipose project from the European Union's SC1-PHE-CORONAVIRUS-2020 programme (grant agreement number 101003688), and consulting fees were paid to his institution by Pfizer and Pfizer Belgium. ACV was supported by the Ministry of Culture and Science of the German State of North Rhine-Westphalia and the German Federal Ministry of Education and Research. TC was supported by the European Union's Horizon 2020 research and innovation programme project PERISCOPE (grant agreement number 101016233). EGl was supported by the Luxembourg National Research Fund. EGr received fees from the German Board of Pharmacists for educational events on COVID-19 and is the president of the German Society for Epidemiology. MK was supported by ZonMw grants number 10430022010001 and number 91216062, and the European Union's Horizon 2020 research and innovation programme project CORESMA (grant agreement number 101003480). NL was supported by European Union's Horizon 2020 research and innovation programme project EpiPose (grant agreement number 101003688), and the Swiss National Science Foundation (project number 176233). MM is a member of UK Independent SAGE. SBM was supported by egePan 01KX7021. MPi was supported by the UK Economic and Social Research Council (ESRC) [ES/S013873/1; ES/T014164/1], the UK Medical Research Council (MRC) [MR/S035818/1], FWO, and Wellcome Trust [209519/Z/17/Z; 106612/Z/14/Z]. BP is a member of the Austrian National Bioethics Commission, and the European Group on Ethics in Science and New Technologies, advising the Austrian Government and the EU Commission respectively. Other research projects in the lab of ESz are partly funded by Merck Healthcare KGaA. All other authors have no competing interests to declare., (© 2021 The Author(s).)