Short-term acute outcomes by clinical and socioeconomic characteristics in adults with SARS-CoV-2: a population-based cohort study focused on the first two years of the COVID-19 pandemic

Background: The COVID-19 pandemic disproportionately affected vulnerable populations in terms of comorbidity and socioeconomic disadvantage, both between and within countries. This retrospective population-based cohort study is part of the Horizon 2020 ORCHESTRA project, was conducted in the Emilia-Romagna (E-R) Region, and aimed to investigate the risk of hospitalization, disease severity and all-cause mortality during the 30 days following SARS-CoV-2 infection. Methods: All adult positive cases notified in E-R from 2020 to 2022 were included. Poisson regression with robust standard error was used to estimate risk ratios for the three outcomes, stratified by sex, pandemic period and adjusted for age, citizenship, deprivation index, risk of hospitalization and death score (RHDS), and vaccination status. Data sources were regional healthcare databases. Supplementary analyses considered citizenship in relation to duration of residency in E-R or aggregated in areas of origin. Results: During the first two years of the pandemic 859,653 E-R residents tested positive for SARS-CoV-2 (47.8% males); 9.6% of them were citizens from high migratory pressure countries (HMPCs). The risk of severe outcomes increased steeply with age, especially in males. RHDS predicted worse outcomes in both sexes while vaccination showed a strong protective effect against all outcomes of acute infection (i.e., recent vaccination was 85% more protective against in-hospital severe disease in both sexes). Immigrants from HPMCs, especially females, showed a higher risk of hospitalization and in-hospital severe disease, in particular those who arrived within 5 years ago from the infection (RR for hospitalization = 1.92, 95%CI = 1.76-2.00 for males, and RR = 2.40, 95%CI = 2.23-2.59 for females), whereas the risk of all-cause mortality was lower compared to residents from low migratory pressure countries (LMPCs) that showed a RR for females of 0.73 (95%CI = 0.59-0.90). Conclusions: The results provided an overall view of course of acute COVID-19 outcomes in E-R and allowed the risk associated with clinical, demographic, and social characteristics to be measured. The findings suggest that, although national and regional public health policies have helped to mitigate the impact of the pandemic in the general population, inequalities in outcomes among persons with comorbidities and social disadvantages remain. Improvements in the appropriateness, effectiveness and equity of public health strategies are needed.