Long-term outcomes after hospital admission for COVID-19 versus seasonal influenza: a cohort study
Background
Previous comparative analyzes of people admitted to hospital for COVID-19 versus influenza assessed the risk of death, hospital readmission, and a limited set of health outcomes up to 6 months after infection. Our objective was to conduct a comparative assessment of both the acute and long-term risks and burdens of a comprehensive set of health outcomes following hospital admission for COVID-19 or seasonal influenza.
Methods
For this cohort study, we used the US Department of Veterans Affairs healthcare databases to analyze data from 81,280 participants admitted to the hospital for COVID-19 between March 1, 2020 and June 30. 2022, and 10,985 participants admitted to hospital for seasonal influenza between October 1, 2015 and February 28, 2019.
Participants were followed for up to 18 months to benchmark the risks and burden of death, a prespecified set of 94 individual health outcomes, ten organ systems, and the overall burden of all organ systems, readmission, and admission. to intensive care throughout the country.
Inverse probability weighting was used to balance baseline characteristics. Cox and Poisson models were used to generate risk estimates on both the relative scale and the absolute scale such as event rate and disability-adjusted life years (DALYs) per 100 people.
Results
Over 18 months of follow-up, compared with seasonal influenza, the COVID-19 group had an increased risk of death (hazard ratio [HR] 1.51 [95% CI: 1.45–1.58]). , corresponding to an excess mortality rate of 8.62 (95% CI: 7.55–9.44) per 100 people in the COVID-19 group compared to the influenza group.
Comparative analyzes of 94 prespecified health outcomes showed that COVID-19 had an increased risk of 68.1% (64 of 94) prespecified health outcomes; seasonal flu was associated with a 6.4% (six of 94) increased risk of prespecified health outcomes, including three of four prespecified lung outcomes.
Analyzes of organ systems showed that COVID-19 had an increased risk in all organ systems except the pulmonary system, for which the risk was highest in seasonal influenza.
The cumulative rates of adverse health outcomes across all organ systems were 615.18 (95% CI: 605.17–624.88) per 100 people in COVID-19 and 536.90 (527.38–544, 90) per 100 people in seasonal influenza, corresponding to an excess rate of 78.72 (95% CI: 66.15–91.24) per 100 people in COVID-19.
The total number of DALYs in all organ systems was 287.43 (95% CI: 281.10–293.59) per 100 people in the COVID-19 group and 242.66 (236.75, 247 .67) per 100 people in the seasonal influenza group, corresponding to 45.03 (95% CI: 37.15–52.90) higher DALYs per 100 people in COVID-19.
Decomposition analyzes showed that in both COVID-19 and seasonal influenza, there was a greater burden of health loss in the post-acute phase than in the acute phase; and comparatively, except for the pulmonary system, COVID-19 had a greater burden of health loss in all other organ systems than seasonal influenza in both the acute and post-acute phases.
Compared with seasonal influenza, COVID-19 also had a higher risk of hospital readmission (excess rate 20.50 [95% CI: 16.10–24.86] per 100 people) and intensive care admission ( excess rate 9.23 [6.68–11.82] per 100 people).
The findings were consistent in analyzes that comparatively evaluated the risks of seasonal influenza versus COVID-19 by individuals’ respective vaccination status and in those admitted to hospital during the pre-delta, delta, and omicron eras.
Figure: Death event rates in COVID-19 and seasonal influenza . Event rates per 100 people are presented for COVID-19 (red) and seasonal influenza (blue). Shaded areas represent 95% CIs. The hazard ratio, rate, and rate difference per 100 people for the periods 0 to 30, 0 to 180, 0 to 360, and 0 to 540 days are also presented.
Interpretation
Although rates of death and adverse health outcomes following hospital admission for seasonal influenza or COVID-19 are high, this comparative analysis shows that hospital admission for COVID-19 was associated with increased long-term risks of death and health outcomes. adverse events in almost all organ systems (except the pulmonary system) and a significant cumulative excess of DALYs than hospital admission for seasonal influenza.
The significant cumulative burden of health loss in both groups calls for greater prevention of hospital admissions from these two viruses and greater attention to the care needs of people with long-term health effects due to seasonal influenza or influenza. SARS-CoV-2 infection.
Funding: US Department of Veterans Affairs
Comments:
New research comparing the viruses that cause flu and COVID-19 shows that people hospitalized with seasonal flu may also suffer long-term negative health effects, especially on the lungs and respiratory tract. The study also found that in the 18 months after infection, patients hospitalized with COVID-19 or seasonal influenza faced a higher risk of death, hospital readmission and other health problems.
Since the COVID-19 pandemic began, extensive research has emerged detailing the virus’s ability to attack multiple organ systems, which could result in a series of long-lasting and often disabling health problems known as long COVID. Now, new research from Washington University School of Medicine in St. Louis and the St. Louis Veterans Affairs Health Care System indicates that people hospitalized with seasonal influenza may also suffer negative health effects through long term, especially in the lungs and airways.
The new study comparing the viruses that cause COVID-19 and the flu also found that in the 18 months after infection, patients hospitalized with COVID-19 or seasonal flu faced a higher risk of death, hospital readmission and health problems. health in many organ systems. Additionally, the time of greatest risk was 30 days or more after initial infection.
"The study illustrates the high number of deaths and health loss after hospitalization for COVID-19 or seasonal influenza," said lead author Ziyad Al-Aly, MD, a clinical epidemiologist at the University of Washington. "It is critical to note that health risks were greatest after the first 30 days of infection. Many people think they are over COVID-19 or the flu after being discharged from the hospital. This may be true for some "But our research shows that both viruses can cause long-lasting illness."
The findings are published in The Lancet Infectious Diseases .
The statistical analysis spanned up to 18 months after infection and included a comparative assessment of the risks of death, hospital admissions and 94 adverse health outcomes involving the body’s major organ systems.
"A review of previous studies on COVID-19 versus flu focused on a limited, short-term set of health outcomes," said Al-Aly, who treats patients within the VA St. Louis Health Care System and is an assistant professor of medicine at the University of Washington. "Our novel approach compared the long-term health effects of a wide range of conditions. Five years ago, it would not have occurred to me to examine the possibility of a ’long flu’ . An important lesson we learned from SARS-CoV-2 is that an infection that was initially thought to only cause a brief illness can also cause chronic illness. This revelation motivated us to look at the long-term outcomes of COVID-19 versus the flu.
"We wanted to know if and to what extent people with the flu also experience long-term health effects," Al-Aly said. "The big answer is that both COVID-19 and the flu caused long-term health problems, and the big moment was realizing that the magnitude of the long-term health loss dwarfed the problems these patients endured in the first place." initial phase" of the infection.
“Long COVID is a much bigger health problem than COVID, and long flu is a much bigger health problem than the flu.”
However, the overall risk and occurrence of death, hospital admissions, and health loss in many organ systems are substantially higher among patients with COVID-19 than among those who have had seasonal influenza, Al-Aly said. "The one notable exception is that the flu poses greater risks to the lung system than COVID-19," he said. "This tells us that the flu is actually more of a respiratory virus , as we’ve all thought for the last 100 years. In comparison, COVID-19 is more aggressive and indiscriminate because it can attack the lung system, but it can also attack any organ system and is more likely to cause fatal or serious conditions affecting the heart, brain, kidneys, and other organs.
The researchers analyzed de-identified medical records in a database maintained by the U.S. Department of Veterans Affairs, the nation’s largest integrated health care delivery system. They evaluated information involving 81,280 patients hospitalized for COVID-19 at some point from March 1, 2020 to June 30, 2022, as well as 10,985 patients hospitalized for seasonal influenza at some point from October 1, 2015 to February 28th. 2019.
The patients represented multiple ages, races and sexes. Regarding both viruses, the vaccination status of the patients did not affect the results. Members of the COVID-19 cohort were hospitalized during the pre-delta, delta, and omicron eras.
Over the overall 18-month study period, patients who had COVID-19 faced a 50% higher risk of death than those with seasonal influenza. This corresponded to about eight more deaths per 100 people in the COVID-19 group than among those with the flu.
Although COVID-19 showed a higher risk of health loss than seasonal influenza, infection with either virus carried a significant risk of disability and illness. The researchers found that COVID-19 exhibited an increased risk in 68% of the health conditions examined across all organ systems (64 of the 94 adverse health outcomes studied), while influenza was associated with an elevated risk in 6% of health conditions (six out of 94) primarily in the respiratory system.
Additionally, over 18 months, COVID-19 patients experienced an increased risk of hospital readmission, as well as admission to an intensive care unit (ICU). For every 100 people in each group, there were 20 more hospital admissions and nine more ICU admissions for COVID-19 than for the flu.
"Our findings highlight the continued need to reduce the risk of hospitalization from these two viruses as a way to alleviate the overall burden of health loss in populations," Al-Aly said. "For both COVID-19 and seasonal influenza, vaccines can help prevent serious illness and reduce the risk of hospitalizations and death. Optimizing vaccination uptake should remain a priority for governments and health systems across the country. "This is especially important for vulnerable populations, such as the elderly and immunocompromised people."
In both COVID-19 and the flu, more than half of the deaths and disabilities occurred in the months after infection, as opposed to the first 30 days, the last of which is known as the acute phase .
"The idea that COVID-19 or the flu are just acute diseases overlooks their broader, long-term effects on human health," Al-Aly said. "Before the pandemic, we tended to belittle most viral infections as inconsequential: ’You’ll get sick and get over it in a few days .’" But we’re finding that’s not everyone’s experience. Some people end up with serious health problems. "In the long term. We need to wake up to this reality and stop trivializing viral infections and understand that they are the main causes of chronic diseases ."
