Background: Nearly 10% of COVID-19 cases will require admission to the intensive care unit (ICU). Our aim was to assess the clinical and microbiological outcomes of secondary infections among critically ill COVID-19 adult patients treated with/without immunomodulation.

Methods: A prospective observational cohort study was performed between 2020 and 2022 at a single ICU. The diagnosis and severity classification were established by the ECDC and WHO criteria, respectively. Eligible patients were included consecutively at admission, and followed for +30 days post-inclusion. Bloodstream-infections (BSIs), ventilator-associated bacterial pneumonia (VAP), and COVID-19-associated invasive pulmonary aspergillosis (CAPA) were defined according to international guidelines. Patient stratification was performed by immunomodulatory therapy administration (dexamethasone, tocilizumab, baricitinib/ruxolitinib). The primary outcome was any microbiologically confirmed major infectious complication, secondary outcomes were invasive mechanical ventilation (IMV) requirement and all-cause mortality.

Results: Altogether, 379 adults were included. At baseline, 249/379 (65.7%) required IMV and 196/379 (51.7%) had a cytokine storm. At +30 days post-inclusion, the rate of any microbiologically confirmed major infectious complication was 151/379 (39.8%), IMV requirement and all-cause mortality were 303/379 (79.9%) and 203/379 (53.6%), respectively. There were no statistically significant outcome differences after stratification. BSI, VAP, and CAPA episodes were mostly caused by Enterococcus faecalis (27/124, 22.1%), Pseudomonas aeruginosa (26/91, 28.6%), and Aspergillus fumigatus (20/20, 100%), respectively. Concerning the primary outcome, Kaplan-Meier analysis showed similar probability distributions between the treatment subgroups (118/299, 39.5% vs. 33/80, 41.3%, log-rank p = 0.22), and immunomodulation was not retained as its independent predictor in multivariate logistic regression.

Conclusions: Secondary infections among critically ill COVID-19 adult patients represent a relevant burden, probably irrespective of immunomodulatory treatment.