Association of COVID-19 Vaccinations With Intensive Care Unit Admissions and Outcome of Critically Ill Patients With COVID-19 Pneumonia in Lombardy, Italy
Authors: Grasselli Giacomo , Zanella Alberto , Carlesso Eleonora , Florio Gaetano , Canakoglu Arif , Bellani Giacomo , Bottino Nicola , Cabrini Luca , Castelli Gian Paolo , Catena Emanuele , Cecconi Maurizio , Cereda Danilo , Chiumello Davide , Forastieri Andrea , Foti Giuseppe , Gemma Marco , Giudici Riccardo , Grazioli Lorenzo , Lombardo Andrea , Lorini Ferdinando Luca , Madotto Fabiana , Mantovani Alberto , Mistraletti Giovanni , Mojoli Francesco , Mongodi Silvia , Monti Gianpaola , Muttini Stefano , Piva Simone , Protti Alessandro , Rasulo Frank , Scandroglio Anna Mara , Severgnini Paolo , Storti Enrico , Fumagalli Roberto , Pesenti Antonio ,   COVID-19 Lombardy ICU Network, Keim Roberto , Vagginelli Federica , Sala Antonello , Merli Guido , Ruggeri Patrizia , Villani Giorgio , Riccio Mario , Zoia Elena , Castelli Antonio , Colombo Riccardo , Rech Roberto , Gnesin Paolo , Coppini Davide , Petrucci Nicola , Antonini Benvenuto , Landolfi Luca , Arnaiz Fernando , Forlini Clarissa , Stefanini Flavia , Micucci Antonio , Marelli Jlenia Alessia , Torresani Francesco , Panzeri Cristina , Paolini Elena , Guzzon Davide , Maderna Laura , Russo Gianluca , Berselli Angela , Biondo Alberto , Montalto Claudio , Bianciardi Leonardo , Della Mura Federica , Marino Giovanni , Zambon Massimo , Subert Matteo , Citerio Giuseppe , Saini Maurizio , Rona Roberto , Pezzi Angelo , Sabbatini Giovanni , Paganini Silvia , Porta Virginia , Benigni Alberto , Bonanomi Ezio , Fabretti Fabrizio , Gritti Paolo , Arachi Giorgio , Raimondi Maurizio , Casazza Alberto , De Filippi Gianluca , Piccoli Francesca , Umbrello Michele , Coppola Silvia , Pozzi Tommaso , Corona Alberto , Bossi Emanuele , Greco Stefano , Besozzi Alessandra , Covello Remo Daniel , Della Morte Mauro , Sangalli Fabio , Gasberti Dario , Maraggia Davide , Motta Alessandro , Agosteo Emiliano , Crottogini Lucia , Leoni Olivia , Tirani Marcello , Carbonara Marco , Crotti Stefania , Fusaris Chiara , Properzi Paolo , Rossi Nicola , Tagliabue Paola , Tubiolo Daniela , Maggio Giuseppe , Pagani Michele , Sciutti Fabio , Bertelli Michele , Militano Carmine Rocco , Morandi Alessandro , Valsecchi Roberto , Albano Giovanni , Barbara Enrico , Ballotta Andrea , Costantini Elena , Greco Massimiliano , Perazzo Paolo , Ceriani Roberto , Ranucci Marco , Resta Marco , Calvi Maria Rosa , Colombo Sergio , Dell'Acqua Antonio , Marino Francesco , Sebastiano Pietro , Sala Giuseppe , Belgiorno Nicolangela , Cosio Rinaldo , Guatteri Luca , Viola Uberto , Galletti Marco , Primerano Vincenzo , Visetti Enrico , Giacomini Matteo , Alborghetti Armando , Bertazzoli Alberto , Bertoni Michele , Mauri Tommaso , Prato Giada , Stocchetti Nino , Vivona Luigi , Waccher Giulia , Filippini Matteo , Latronico Nicola , Giani Marco , Pozzi Matteo 
Published: October 2022

Importance

Data on the association of COVID-19 vaccination with intensive care unit (ICU) admission and outcomes of patients with SARS-CoV-2–related pneumonia are scarce.

Objective

To evaluate whether COVID-19 vaccination is associated with preventing ICU admission for COVID-19 pneumonia and to compare baseline characteristics and outcomes of vaccinated and unvaccinated patients admitted to an ICU.

Design, Setting, and Participants

This retrospective cohort study on regional data sets reports: (1) daily number of administered vaccines and (2) data of all consecutive patients admitted to an ICU in Lombardy, Italy, from August 1 to December 15, 2021 (Delta variant predominant). Vaccinated patients received either mRNA vaccines (BNT162b2 or mRNA-1273) or adenoviral vector vaccines (ChAdOx1-S or Ad26.COV2). Incident rate ratios (IRRs) were computed from August 1, 2021, to January 31, 2022; ICU and baseline characteristics and outcomes of vaccinated and unvaccinated patients admitted to an ICU were analyzed from August 1 to December 15, 2021.

Exposures

COVID-19 vaccination status (no vaccination, mRNA vaccine, adenoviral vector vaccine).

Main Outcomes and Measures

The incidence IRR of ICU admission was evaluated, comparing vaccinated people with unvaccinated, adjusted for age and sex. The baseline characteristics at ICU admission of vaccinated and unvaccinated patients were investigated. The association between vaccination status at ICU admission and mortality at ICU and hospital discharge were also studied, adjusting for possible confounders.

Results

Among the 10 107 674 inhabitants of Lombardy, Italy, at the time of this study, the median [IQR] age was 48 [28-64] years and 5 154 914 (51.0%) were female. Of the 7 863 417 individuals who were vaccinated (median [IQR] age: 53 [33-68] years; 4 010 343 [51.4%] female), 6 251 417 (79.5%) received an mRNA vaccine, 550 439 (7.0%) received an adenoviral vector vaccine, and 1 061 561 (13.5%) received a mix of vaccines and 4 497 875 (57.2%) were boosted. Compared with unvaccinated people, IRR of individuals who received an mRNA vaccine within 120 days from the last dose was 0.03 (95% CI, 0.03-0.04; P &amp;lt; .001), whereas IRR of individuals who received an adenoviral vector vaccine after 120 days was 0.21 (95% CI, 0.19-0.24; P &amp;lt; .001). There were 553 patients admitted to an ICU for COVID-19 pneumonia during the study period: 139 patients (25.1%) were vaccinated and 414 (74.9%) were unvaccinated. Compared with unvaccinated patients, vaccinated patients were older (median [IQR]: 72 [66-76] vs 60 [51-69] years; P &amp;lt; .001), primarily male individuals (110 patients [79.1%] vs 252 patients [60.9%]; P &amp;lt; .001), with more comorbidities (median [IQR]: 2 [1-3] vs 0 [0-1] comorbidities; P &amp;lt; .001) and had higher ratio of arterial partial pressure of oxygen (Pao2) and fraction of inspiratory oxygen (FiO2) at ICU admission (median [IQR]: 138 [100-180] vs 120 [90-158] mm Hg; P = .007). Factors associated with ICU and hospital mortality were higher age, premorbid heart disease, lower Pao2/FiO2 at ICU admission, and female sex (this factor only for ICU mortality). ICU and hospital mortality were similar between vaccinated and unvaccinated patients.

Conclusions and Relevance

In this cohort study, mRNA and adenoviral vector vaccines were associated with significantly lower risk of ICU admission for COVID-19 pneumonia. ICU and hospital mortality were not associated with vaccinated status. These findings suggest a substantial reduction of the risk of developing COVID-19–related severe acute respiratory failure requiring ICU admission among vaccinated people.