Flu or COVID-19: Which Virus Poses the Greater Risk to Vulnerable People?
As respiratory viruses continue to circulate, one question regularly returns: for vulnerable people, is influenza or COVID-19 the greater threat? The answer is now more nuanced than it was during the early years of the pandemic. Both infections can cause severe disease, but their impact varies according to age, underlying medical conditions, immunity, vaccination status and the level of viral circulation.
Recent evidence suggests that there is no universal rule that makes one of these viruses consistently more dangerous than the other for every vulnerable person.
COVID-19 remains an important threat for older adults
According to the World Health Organization, older adults remain particularly vulnerable to severe COVID-19. People aged 65 and over accounted for almost 90% of COVID-19 deaths reported to WHO in 2025.
At the same time, WHO notes that increasing population immunity has substantially reduced the severity of COVID-19 compared with the first years of the pandemic. However, recent data indicate that among older adults, COVID-19 mortality rates can now be comparable to those associated with seasonal influenza and, in some settings, even higher.
In other words, COVID-19 no longer has the same risk profile it had in 2020 or 2021, but it should not be considered a harmless respiratory infection for vulnerable people.
Influenza can also cause severe complications
Influenza remains an important cause of hospitalization and death, particularly among older adults, people with chronic diseases and those with weakened immune systems.
In France, the official assessment of the 2025-2026 season found that influenza activity was low to moderate in primary care but high in hospitals. The epidemic was driven exclusively by influenza A viruses and occurred between December 2025 and mid-February 2026.
Santé publique France recorded 1,382 severe influenza cases reported by participating intensive-care units. The impact on mortality was also substantial at the beginning of 2026. At the epidemic peak, 7.3% of deaths recorded through electronic death certification were associated with influenza.
The total number of influenza deaths reported through this system nevertheless remained below the previous season, at 4,389 compared with 4,925.
These figures show that seasonal influenza remains a significant threat to vulnerable people, even while COVID-19 continues to circulate.
What do direct comparisons show?
Direct comparisons become particularly informative when researchers examine hospitalized patients.
A 2025 study published in Frontiers in Public Health compared adults hospitalized with COVID-19 and influenza and found differences in mortality across age groups. Among patients aged 65 to 74 and those aged 75 and older, mortality was higher in the COVID-19 group than in the influenza group during the study period.
Among patients aged 75 and older, one-year mortality was 42.16% in the COVID-19 cohort compared with 21.59% in the influenza cohort.
However, these figures must be interpreted carefully. The study involved hospitalized patients rather than the general population, and its findings reflect a particular period and healthcare setting.
Another prospective study published in 2026 examined older adults who were hospitalized with acute respiratory symptoms. In this population, whose mean age was 81, 30-day mortality was 8.4% among patients with COVID-19 and 2.9% among those with influenza.
Again, these findings do not mean that COVID-19 is always more dangerous than influenza. They describe a specific hospitalized population and a specific clinical context.
The individual risk profile matters enormously.
Who is most vulnerable?
Many of the major risk factors for severe disease are shared by influenza and COVID-19.
The WHO identifies older adults and people with chronic cardiovascular or respiratory diseases, diabetes, kidney disease, liver disease or neurological conditions as higher-risk groups. People with weakened immune systems are also particularly vulnerable.
Patients receiving certain immunosuppressive treatments can face a substantially higher risk of severe respiratory infections. An infection that remains relatively mild in a healthy young adult can develop into pneumonia, respiratory failure or other complications in a vulnerable patient.
Pregnancy is another situation in which the risk of complications from respiratory infections may be increased.
COVID-19: the risk has declined, but has not disappeared
The evolution of SARS-CoV-2 has significantly changed the respiratory-virus landscape. Immunity acquired through previous infection and vaccination has reduced the risk of severe disease across the population.
However, this protection is not uniform. Older and immunocompromised people may have weaker protection against severe disease, and protection can decline over time.
WHO data also show that most people hospitalized with COVID-19 have at least one underlying medical condition. In the United States, more than 90% of people hospitalized with COVID-19 since 2023 had at least one underlying condition.
Influenza, meanwhile, remains strongly seasonal and can place substantial pressure on healthcare systems every year.
Vaccination remains a key preventive measure
The comparison between the two viruses should not obscure an important point: for vulnerable people, preventing severe disease matters more than determining which virus is “worse.”
An ECDC analysis of the 2024-2025 season in the European Union and European Economic Area estimated that influenza vaccination prevented approximately 26% to 41% of influenza-related hospitalizations among adults aged 65 and older, depending on the country and modelling assumptions.
For COVID-19, the projected reduction in hospitalizations among the same age group was estimated at 14% to 20%.
These estimates depend on vaccination coverage, viral circulation, vaccine effectiveness and changes in population immunity. They should therefore not be interpreted as evidence that one vaccine is inherently “better” than the other.
In France, Santé publique France estimated influenza vaccination coverage at 56.7% among people aged 65 and older at the end of the 2025-2026 vaccination campaign.
So, flu or COVID-19?
The answer depends largely on the person’s medical profile and the epidemiological context.
Influenza can cause serious complications, particularly among older adults and people with chronic diseases. It can lead to pneumonia, worsen heart or respiratory failure and contribute to cardiovascular complications.
COVID-19 also retains substantial potential to cause severe disease among older and immunocompromised people. Recent WHO data indicate that among older adults, COVID-19 mortality can be comparable to seasonal influenza and, in some settings, higher.
It is therefore more accurate to regard both infections as important risks for vulnerable populations rather than trying to identify one universal “winner.”
For an older or immunocompromised person, respiratory symptoms deserve particular attention, especially when accompanied by difficulty breathing, chest pain, confusion, severe weakness or rapidly worsening symptoms.
The main public-health message is straightforward: for vulnerable people, the most important issue is not simply whether influenza or COVID-19 is more dangerous. The priority is to reduce the risk of severe disease through recommended vaccination, appropriate management of chronic conditions, early medical assessment when indicated and prevention measures adapted to current viral circulation.
The situation has changed substantially since the first years of the pandemic, but neither influenza nor COVID-19 should be considered harmless for people at highest risk.
