Acute and Longterm Health Implications of Covid-19 versus Seasonal Influenza

December 22, 2023

In a research paper published this month, researchers utilized data from the Department of Veterans Affairs to compare both acute and long-term risks and health outcomes following hospital admission for COVID-19 and the seasonal flu.

Health data from over 81,000 COVID-19 patients hospitalized between March 1, 2020, and June 30, 2022, was compared to data from just under 11,000 patients hospitalized for seasonal influenza between October 1, 2015, and February 28, 2019. Both COVID-19 and seasonal flu patients were admitted to the hospital with an admission diagnosis within five days before or within 30 days after positive test results.

Within the seasonal influenza group, 76% were diagnosed with influenza type A. COVID-19 participants were separated into three groups: pre-delta, delta, and omicron, depending on which months they were admitted into the hospital for infection. Researchers followed up with participants for up to 18 months, evaluating their profiles against 94 pre-specified health outcomes and other factors, including organ systems (cardiovascular, coagulation and hematological, fatigue, gastrointestinal, kidney, mental health, metabolic, musculoskeletal, neurological, and pulmonary).

Researchers identified two key findings through their analysis. For both COVID-19 infection and seasonal flu infections, there was an increased burden of disease and health loss during the post-acute phase versus the acute phase of infection. COVID-19 also had a higher burden of disease across all organ systems in both the acute and post-acute phases besides the pulmonary system. COVID-19 patients had an increased risk of hospital readmission and admission into intensive care; hospital admission for COVID-19 was also associated with a higher risk of death. Over 18 months of follow-up, COVID-19 patients had an increased risk of death versus the influenza group. Compared to the seasonal flu, COVID-19 had a higher risk of death and risk to all organs except for the pulmonary system, regardless of both COVID-19 and seasonal influenza vaccination status.

The results of the study suggest that while “both viruses exact a substantial toll of health loss across multiple organ systems… comparative evaluation of the risks of adverse health outcomes across ten organ systems suggests that seasonal influenza is more of a respiratory virus than SARS-CoV-2 and that the latter is a more multi-systemic virus than seasonal influenza.” Furthermore, the results of the analysis imply that COVID-19 infections have a “longer-term risk horizon for organ damage than seasonal influenza.” Providing post-acute care has the ability to improve health outcomes and reduce hospital readmissions.