COVID-19 hospitalization linked to greater long-term health risks than seasonal influenza

By Dr. Sanchari Sinha Dutta, Ph.D.Dec 18 2023

A study published in The Lancet Infectious Diseases reveals that the long-term risk of death and health adversities associated with coronavirus disease 2019 (COVID-19)-related hospitalization is higher than that associated with seasonal influenza-related hospitalization.

Study: Long-term outcomes following hospital admission for COVID-19 versus seasonal influenza: a cohort study. Image Credit: Andrii Vodolazhskyi / Shutterstock

Background

Like severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen of the most recent COVID-19 pandemic, influenza viruses are enveloped RNA viruses that cause mild to severe respiratory infections. Both COVID-19 and influenza are associated with a higher risk of adverse health outcomes and mortality.

Previous studies comparing health outcomes between hospitalized COVID-19 and influenza patients demonstrate that SARS-CoV-2 infection is associated with a higher risk of death and long-term health adversities than seasonal influenza infection up to six months following infection.

In this study, scientists have investigated both acute and long-term risks of death, healthcare utilization, and a comprehensive set of 94 health outcomes over a period of 18 months in patients who were admitted to the hospitals due to COVID-19 or seasonal influenza.

Study design

The study population included 81,280 COVID-19 patients admitted to the hospital between 2020 and 2022 and 10,985 seasonal influenza patients hospitalized between 2015 and 2019. The patient data were obtained from the US Department of Veterans Affairs healthcare databases. The patients were followed up for 18 months.

The parameters assessed in the study included acute and long-term risks and burdens of death, a comprehensive set of 94 health outcomes, ten organ systems, overall burden across all organ systems, hospital readmission, and admission to the intensive care unit (ICU). Moreover, disability-adjusted life-years (DALYs) per 100 persons were estimated using appropriate statistical methods. The risks were evaluated at 30 days, 180 days, 360 days, and 540 days after hospital admission.    

Important observations

The study found a higher absolute mortality rate among hospitalized COVID-19 patients than hospitalized seasonal influenza patients at each tested time point. Specifically, COVID-19 was associated with an excess mortality rate of 8.62 per 100 persons compared to influenza infection at 540 days post-hospitalization.

During the entire 540-day follow-up period, COVID-19 patients showed a significantly increased risk of 64 out of 94 examined health outcomes, including cardiovascular, coagulation and hematological, fatigue, gastrointestinal, kidney, mental health, metabolic, musculoskeletal, neurological, and pulmonary outcomes.  

In contrast, patients with influenza infection showed an increased risk of six health outcomes, including chest pain, increased heart rate, type 1 diabetes, and three of four pulmonary outcomes (cough, hypoxemia, and shortness of breath).

Considering health adversities across all organ systems, COVID-19 was associated with an excess rate of 78.7 per 100 persons compared to influenza infection during the entire follow-up period. Moreover, COVID-19 was associated with a higher disability-adjusted life years of 45.03 per 100 persons compared to influenza infection.    

Considering acute and long-term health outcomes, more than 50% of COVID-19- and influenza-related adversities in all examined organ systems except for the gastrointestinal system occurred in the post-acute phase of infection. However, COVID-19 patients showed comparatively higher adversities in all organs except for the pulmonary system in both acute and post-acute phases of infection.

Compared to patients with influenza, COVID-19 patients showed higher risks of hospital readmission and ICU admission at all tested time points.

During the pre-delta, delta, and omicron waves, COVID-19-related hospitalization was associated with higher risks of mortality, health adversities across all organs except for the pulmonary system, hospital readmission, and ICU admission compared to influenza-related hospitalization. Across all three pandemic waves, the disease burden was higher in the post-acute infection phase than in the acute phase.

The risks of mortality and health adversities due to COVID-19 remained higher than influenza-related risks regardless of the patients' COVID-19 and influenza vaccination status.

Study significance

The study finds that hospitalized COVID-19 patients have higher long-term risks of mortality, health adversity, and healthcare utilization than hospitalized influenza patients. Compared to influenza, COVID-19 is associated with a higher risk of health adversities in nearly all organs except the pulmonary system. Moreover, COVID-19 hospitalization is associated with higher disability-adjusted life years compared to influenza hospitalization.

As mentioned by the scientists, long-term health outcomes of patients with influenza or SARS-CoV-2 infection should be carefully monitored in order to prevent health adversities and reduce mortality risk.