].Emerging infectious diseases are a  growing threat, through population growth, increased trade and travel,  urbanization, deforestation, and climate change [[1]].  Clinical research in response to emerging infectious diseases is  challenging; selecting and contracting the appropriate study sites for a  trial is time consuming, and often too few patients can be timely  recruited to acquire high-quality evidence about the best treatment  strategies [[2]].  In 2014, the EU-funded PREPARE project (Platform foR European  Preparedness Against (Re-)emerging Epidemics) was initiated to rapidly  respond to severe infectious diseases outbreaks. It initiated two  adaptive platform trials, the REMAP-CAP [[3]] and the ALIC4E trial [[4]],  determining the effectiveness of multiple treatment strategies for a  single disease. The REMAP-CAP trial was designed for a pandemic of  severe community-acquired pneumonia and expanded globally during the  COVID-19 pandemic. It has already delivered 10 important conclusions for  better treatment of COVID-19 [[3]

].Antimicrobial  resistance (AMR), on the other hand, is a more silent pandemic, which  further augments the burden of infectious diseases. Development of new  antibacterial agents has slowed, due to a combination of low return on  investment and challenging clinical trial conditions [[5]].  Since the 2000s, national and global efforts have been initiated to  promote antibiotic development, including the setup of public–private  partnerships, like COMBACTE (Combatting Bacterial Resistance in Europe),  funded by the EU's Innovative Medicines Initiative. Since 2013,  COMBACTE has focused on rapid and efficient development of new AMR  prevention and treatment strategies, through site selection  streamlining, real world data collection for patient enrichment and  pathogen prioritization [[6]], and improvement of clinical trial efficiency through innovative methodological and statistical approaches [[7]

A  clinical research network applying different innovative concepts could  enhance research efficiency to address both the growing threat of  (re-)emerging infectious diseases and the increasing burden of AMR.  Therefore, the academic partners from PREPARE, COMBACTE, and other  EU-funded collaborative networks (see Acknowledgements)  combined their strengths to establish the European Clinical Research  Alliance on Infectious Diseases (Ecraid) Foundation in January 2022—a  clinical research network that aims to efficiently generate rigorous  evidence to improve the diagnosis, prevention, and treatment of  infections in Europe through innovative solutions. Here we discuss the  advantages and challenges of the implementation of Perpetual  Observational Studies (POS).