Prevalence, risk factors, and outcomes of secondary infections among hospitalized patients with COVID-19 or post-COVID-19 conditions in Victoria, 2020-2023

Hugh C Murray; Michael Muleme; Darcie Cooper; Bridgette J McNamara; Mohammad A Hussain; Caroline Bartolo; Daniel P O'Brien; Eugene Athan

doi:10.1016/j.ijid.2024.107078

Prevalence, risk factors, and outcomes of secondary infections among hospitalized patients with COVID-19 or post-COVID-19 conditions in Victoria, 2020-2023

Int J Infect Dis. 2024 May 1:145:107078. doi: 10.1016/j.ijid.2024.107078. Online ahead of print.

Authors

Hugh C Murray¹, Michael Muleme², Darcie Cooper³, Bridgette J McNamara⁴, Mohammad A Hussain⁵, Caroline Bartolo⁶, Daniel P O'Brien⁷, Eugene Athan⁸

Affiliations

¹ Department of Infectious Diseases, Barwon Health, Geelong, Australia; Barwon Southwest Public Health Unit, Barwon Health, Geelong, Australia.
² Barwon Southwest Public Health Unit, Barwon Health, Geelong, Australia; Centre for Innovation in Infectious Disease and Immunology Research, Deakin University, Geelong, Australia. Electronic address: Michael.Muleme@barwonhealth.org.au.
³ Centre for Innovation in Infectious Disease and Immunology Research, Deakin University, Geelong, Australia; Deakin University, Institute for Mental and Physical Health and Clinical Translation (IMPACT), School of Medicine, Geelong, Australia.
⁴ Barwon Southwest Public Health Unit, Barwon Health, Geelong, Australia; Centre for Innovation in Infectious Disease and Immunology Research, Deakin University, Geelong, Australia; Centre for Epidemiology and Biostatistics, The University of Melbourne, Melbourne, Australia.
⁵ Barwon Southwest Public Health Unit, Barwon Health, Geelong, Australia; Deakin University, Institute for Mental and Physical Health and Clinical Translation (IMPACT), School of Medicine, Geelong, Australia.
⁶ Department of Infectious Diseases, Barwon Health, Geelong, Australia; Barwon Southwest Public Health Unit, Barwon Health, Geelong, Australia; Deakin University, Institute for Mental and Physical Health and Clinical Translation (IMPACT), School of Medicine, Geelong, Australia.
⁷ Department of Infectious Diseases, Barwon Health, Geelong, Australia; Barwon Southwest Public Health Unit, Barwon Health, Geelong, Australia; Department of Medicine and Infectious Diseases, Royal Melbourne Hospital, University of Melbourne, Melbourne, Australia.
⁸ Department of Infectious Diseases, Barwon Health, Geelong, Australia; Barwon Southwest Public Health Unit, Barwon Health, Geelong, Australia; Centre for Innovation in Infectious Disease and Immunology Research, Deakin University, Geelong, Australia; School of Medicine, Deakin University, Geelong, Australia.

PMID: 38697606
DOI: 10.1016/j.ijid.2024.107078

Abstract

Objectives: Estimates of secondary infections are variedly reported, with few studies done in Australia. We investigated the occurrence and impact of secondary infections complicating COVID-19 and post-COVID-19 admissions in Victoria, Australia, 2020-2023.

Methods: We used linked population-wide data sets and specific International Classification of Disease, 10th Revision codes to identify and estimate the occurrence of secondary infections. Using hospital/intensive care unit length of stay in negative binomial regression and mortality, we examined the impact of secondary infections.

Results: Secondary infections were identified in 6.9% (13,467 of 194,660) of COVID-19 and post-COVID-19 admissions: 6.0% (11,651 of 194,660) bacterial, 0.9% (1691 of 194,660) viral, and 0.2% (385 of 194,660) fungal. Prevalence was highest during the pre-Delta (10.4%) and Omicron-BA2 (8.1%) periods. Sepsis and pneumonia were the most reported syndromes; the occurrence of sepsis declined gradually over time. The odds of secondary infections were higher among the ≥70-year-olds (adjusted odds ratio (aOR) 3.76, 95% confidence interval [CI] 3.43-4.14, vs 20-29-year-olds), individuals with chronic conditions (aOR 3.15, 95% CI 2.88-3.45, vs those without), the unvaccinated (aOR 1.59, 95% CI 1.45-1.75), and the lowest socioeconomic group (aOR 1.12, 95% CI 1.05-1.19). Patients with secondary infections had 2.43 times longer hospital length of stay and 9.60 times longer intensive care unit length of stay than those without secondary infections. The mortality risk was 2.17 times higher in those with secondary infections.

Conclusions: Secondary infections occurred in 69 per 1000 COVID-19-associated hospital admissions in Victoria, mostly in high-risk groups, and were associated with severe outcomes.

Keywords: COVID-19; Pathogens; Secondary infections; Severity outcomes; Syndromes.