Long-COVID and Long-influenza

Research shows that hospitalised influenza patients can also have long-term effects, especially in lungs and respiratory tract; but long-COVID has worse outcomes.

SARS-CoV-2 and influenza cause long-term complications

A new study comparing viruses causing COVID-19 and influenza revealed that, in the 18 months following infection, patients hospitalised for COVID-19 or seasonal influenza faced a higher risk of death, hospital readmission and health problems. In addition, the time of highest risk turned out to be 30 days after the initial infection. According to research leader Dr. Ziyad Al-Aly, a clinical epidemiologist at Washington University, this is a key aspect of the research results.

The statistical analysis covered up to 18 months post-infection and included a comparative assessment of the risks of death, hospitalisation and 94 adverse health outcomes involving major systems. This is an innovative aspect of the research, because in the past the long-term outcomes of influenza have always been limited to a few conditions. According to the authors, it is necessary for physicians to understand that a viral infection often has the potential to lead to chronic diseases. 

The research aim was to investigate whether (and to what extent) people suffering from influenza experience long-term health effects. They identified that both COVID-19 and influenza lead to long-term health problems in many cases.

However, the overall risk and occurrence of death, hospitalisation and multi-organ health problems are substantially higher among patients with COVID-19 than among those who have had seasonal influenza. According to the researchers, the exception lies in that influenza poses higher risks for the pulmonary system than COVID-19. The researchers argue that such results show that the influenza virus is specifically a respiratory virus, whereas SARS-CoV-2 is more aggressive and indiscriminate.

COVID-19 has worse chronic consequences than influenza

Researchers analysed de-identified medical records from a database maintained by the US Department of Veterans Affairs, the nation's largest integrated health care system. They evaluated information on 81,280 patients admitted for COVID-19 during the period between 1 March 2020 and 30 June 2022, as well as 10,985 patients admitted for seasonal influenza during the period between 1 October 2015 and 28 February 2019.

For both viruses, the vaccination status of the patients did not affect the results. Patients in the COVID-19 cohort were admitted during the pre-delta, delta and omicron eras.

During the entire study period, COVID-19 patients faced a 50 per cent higher risk of death than seasonal influenza patients. This corresponds to approximately eight more deaths per 100 people in the COVID-19 group than in those with influenza.

Although COVID-19 showed a higher risk of health loss than seasonal influenza, infection with both viruses carried a significant risk of disability and illness. The researchers found that COVID-19 showed a 68% increased risk of health conditions examined in all organs (64 out of 94 negative health outcomes studied), while influenza was associated with a 6% elevated risk for health conditions (6 out of 94), especially in the respiratory system.

In addition, over an 18-month period, COVID-19 patients experienced an increased risk of hospital readmission and admission to an intensive care unit. For every 100 people in each group, there were 20 more hospital admissions and 9 more intensive care unit admissions in the COVID-19 group than in the influenza group.

According to the researchers, there is a need to reduce the risk of hospitalisation for these two viruses. For both COVID-19 and seasonal influenza, vaccination can help prevent serious illness and reduce the risk of hospitalisation and death. Optimising vaccination uptake must remain a priority for governments and health systems worldwide. According to the authors, this is especially important for vulnerable populations such as the elderly and immunocompromised people.

COVID-19 remains a significantly greater threat even in the post-Omicron era and as vaccination becomes more widespread. These findings indicate the need for further research into the pathophysiology of post-viral syndromes and emphasise the importance of pharmacological and non-pharmacological therapeutic approaches to manage the long-term complications of both viral infections. In summary, the study provides a detailed picture of the long-term consequences of COVID-19 and seasonal influenza, encouraging further investigation and reflection in the medical community.

  1. Xie Y, Choi T, Al-Aly Z. Long-term outcomes following hospital admission for COVID-19 versus seasonal influenza: a cohort study. The Lancet Infectious Diseases. Dec. 14, 2023. DOI: https://doi.org/10.1016/S1473-3099(23)00684-9