Cohort profile: a multicenter European study of acute respiratory infections: the MERMAIDS-ARI 2.0 cohort study

PurposeMulti-centre EuRopean study of MAjor Infectious Disease Syndromes - Acute Respiratory Infections (MERMAIDS-ARI) cohort study is a European prospective cohort study. It was originally launched in 2016 as MERMAIDS-ARI to study acute respiratory infections. When the COVID-19 pandemic hit, the study re-started inclusion under an amended protocol as MERMAIDS-ARI 2.0 focusing on SARS-CoV-2. The objectives of this study were to describe the disease spectrum, clinical features, and outcomes of SARS-CoV-2 infections in hospital care, to determine relevant risk factors and the assess prevalence and within hospital spread compared to other respiratory infections. An important second objective was to establish an extensive biobank supplemented with detailed clinical data to be able to address future virological, immunological, and clinical research questions. MethodsPatients with either 1) ARI presenting to hospital care during the SARS-CoV-2 epidemic (including both COVID-19 and non-COVID-19 patients) or 2) confirmed COVID-19 infection, but with atypical presentation (non-ARI) or with nosocomial acquisition were included. Clinical data and biological samples were collected on enrolment day and repeatedly thereafter until discharge. A subset of COVID-19 patients was also followed up to 12 months post-discharge to study clinical recovery and long-term sequelae. Findings to dateIn total 297 patients from 8 countries and 11 sites were recruited between June 2020 and September 2021. We reached high sample completeness for most sample types (>97% for single samples and >86% for serial samples). 294 (99.0%) patients were admitted to hospital with SARS-CoV-2. The population primarily consists of patients (median age 61 years) of Caucasian ethnicity, with the majority being male (62.0%) and having [≥]1 comorbidities (67.3%). The median hospital stay was 10 days, and most patients (87.5%) received treatment with systemic corticosteroids and respiratory support (81.4%). A total of 64 (21.7%) patients were admitted to the Intensive Care Unit (ICU), and 6.5% died during hospitalization. Long-term follow-up of 94 patients revealed that most individuals resumed their regular activities and work within three months, with improvements observed in mobility and personal care over time. Instances of severe and extreme pain and anxiety were rarely reported ([≤]1.1%). ConclusionThis pan-European study offers a valuable resource for conducting in-depth virological, immunological, and pathophysiological investigations pertaining to SARS-CoV-2.