Impatto del COVID-19 dopo l’inizio della vaccinazione in gruppi di popolazione a rischio, tra cui gli immunocompromessi. Italia 2021-2023

Introduction In Italy, the evidence on the impact of COVID-19 on at-risk population groups is limited. This work details the risks of hospitalization and death from COVID-19 among various at-risk categories after the start of vaccination, including the immunocompromised population, in Italy from 2021 to 2023. Materials and methods This study utilized data from the Integrated COVID-19 Surveillance to obtain the number of hospitalizations and deaths, and data from the National Registry of COVID-19 Vaccinations to identify at-risk population categories. A record linkage was performed between the two data sources using the tax code as a unique identifier. The following health conditions were considered at risk: immunocompromised, hemodialysis, renal failure, nursing home residents, solid tumors, multiple pathologies, and an "other" at-risk category. The risk of hospitalization and death after vaccination was calculated for each category using a Poisson regression model adjusted for age group, gender, geographic area, and with the number of vaccinated individuals as an offset variable. Results The highest risk of hospitalization post-vaccination was observed in hemodialysis patients (Incidence Risk Ratio, IRR = 7.1), followed by those with renal failure (IRR = 3.51) and the immunocompromised (IRR=3.23). Similarly, the risk of death among the vaccinated was higher for hemodialysis patients (IRR=8.24), followed by the immunocompromised (IRR=3.93) and those with renal failure (IRR = 3.26). Discussion and conclusions Among the at-risk categories analyzed, the results show that the greatest risk of hospitalization and death from COVID-19 is among those on hemodialysis, those with renal failure, and the immunocompromised. All subjects presenting a risk category, except those in the "other" category, had a higher risk of hospitalization and death from COVID-19 compared to those with no reported risk category. This study represents an initial national-level analysis describing the impact of COVID-19 in terms of risk of hospitalization and death among at-risk population groups