Μake us preferred on Google Seasonal flu has arrived, bringing the familiar illnesses that accompany every winter. And, as is now widely understood, some people are more vulnerable than others.
Age and chronic health conditions, however, are not the only factors that increase the risk of complications. Harmful everyday habits can also play a role, with smoking at the top of the list.
As Dr. Stamatoula Tsikrika explains in TA NEA, health systems across Europe are preparing for the expected epidemiological rise in seasonal influenza cases as temperatures fall. Tsikrika served as chair of the European Respiratory Society’s Tobacco Control Committee from 2023 to 2026 and is secretary and treasurer of the UEMS Pneumology Section.
Despite major advances in medicine and the implementation of vaccination programs among the general population, influenza remains a serious public health problem. According to the World Health Organization (WHO), annual influenza epidemics cause millions of cases of severe illness worldwide and are estimated to be associated with 290,000 to 650,000 deaths each year, primarily due to respiratory complications.
Tsikrika also notes that the severity and clinical outcome of influenza infection, regardless of the viral strain, vary widely among patients.
“Various factors, such as age, preexisting immunity, the presence of chronic diseases and overall health status, have a statistically significant impact on the risk of developing complications. However, the crucial role of specific individual behaviors, such as smoking, is less frequently recognized, even though they can affect both susceptibility to viral infections and the severity of the disease.”
More Severe Illness and Complications
Smoking is unquestionably one of the most significant modifiable causes of damage to the respiratory system.
“The toxic substances contained in cigarette smoke cause chronic structural and functional changes to the airways and lung parenchyma. The resulting damage to the respiratory epithelium leads to dysfunction of defense mechanisms and disruptions to the immune response that can weaken the body’s ability to effectively fight viruses and bacterial pathogens,” explains Tsikrika, who is also scientific director of the Smoking Cessation and Follow-Up Clinic at Athens’ Sotiria Hospital.
As a result, she adds, smokers may be more susceptible to respiratory infections, depending on the intensity and duration of their smoking habit.
“In particular, they may face an increased risk of more severe illness and complications, potentially even requiring admission to intensive care units.”
The problem becomes even more serious among chronic smokers, many of whom already have chronic obstructive pulmonary disease (COPD), cardiovascular disease or other conditions that reduce the functional reserve of vital organs.
“In these patients, even an influenza infection can significantly worsen their health, contributing to persistent morbidity after the acute phase of the illness,” she warns.
The Role of Smokers’ Hands
Tsikrika also points to another behavioral factor that can contribute to the transmission of infections. Repeatedly bringing the hands into contact with the mouth and nose while smoking can facilitate the transfer of pathogenic microorganisms to the mucous membranes.
Of particular concern is smokers’ increased risk of secondary bacterial infections following influenza.
“The combination of viral damage to the respiratory epithelium and the disruption of defense mechanisms caused by smoking can create more favorable conditions for bacterial pathogens to become established and multiply,” Tsikrika says.
“Among these, pneumococcus is the most common cause of community-acquired pneumonia, while Staphylococcus aureus is also associated with severe cases of post-influenza bacterial pneumonia.”
Vaccination as an Opportunity to Quit Smoking
Against this backdrop, Tsikrika stresses that the cornerstone of influenza prevention is annual flu vaccination.
She notes that, according to recommendations from the WHO and international scientific societies, vaccination is the most important measure for preventing severe illness and helps reduce hospitalizations and deaths.
Particular emphasis is placed on vaccinating people at increased risk of complications, including older adults, patients with chronic illnesses, pregnant and breastfeeding women, and health care professionals, in accordance with current national recommendations.
“However, an equally important pillar of prevention is smoking cessation and addressing nicotine dependence through smoking cessation clinics,” Tsikrika says.
“Although many smokers believe that the benefits of quitting become noticeable only over the long term, smoking cessation gradually brings significant positive changes to health. Over time, the functioning of the respiratory system’s defense mechanisms improves and the body’s exposure to carcinogenic substances is reduced. In the long term, quitting smoking reduces the risk of respiratory and cardiovascular diseases, malignancies and premature mortality.”
For this reason, Tsikrika notes, the beginning of seasonal flu season and the increased number of people seeking influenza vaccination create an important opportunity for intervention by health professionals with specialized knowledge of smoking cessation.
“A vaccination appointment can be used not only to prevent influenza, but also to begin a meaningful conversation,” she says.
“This approach becomes even more valuable when accompanied by individualized counseling and evidence-based pharmacotherapy, which significantly increase the chances of successful, long-term smoking cessation, making a substantial contribution to protecting both respiratory and overall health.”
The ‘Other’ Bad Habits
Smoking, meanwhile, is not the only harmful habit that weakens the immune system.
Alcohol reduces the ability of white blood cells to multiply and destroy viruses, while an earlier study found that chronic alcohol abuse reduces specialized CD8+ T cells in the lungs, which are essential for fighting the influenza virus.
Sleep deprivation also appears to undermine the immune system, as the body is forced to produce fewer cytokines — proteins that regulate the immune response.
Diet also belongs on the list. A balanced diet helps strengthen the body’s defenses, but loses that protective quality when people frequently give in to sugary and salty indulgences.
