Lung Cancer Risk After Respiratory Infections: What You Need to Know
Severe respiratory infections like COVID-19 and influenza may increase the risk of developing lung cancer, but vaccination significantly reduces this risk, according to recent research. A study published in Cell reveals that these infections can “reprogram” immune cells in the lungs, creating an environment conducive to tumor growth.
How Infections Prime the Lungs for Cancer
Researchers at the University of Virginia (UVA) School of Medicine, led by Dr. Jie Sun, investigated the long-term effects of respiratory infections on lung cancer risk. Their findings indicate that severe infections cause lasting inflammation in the lungs, making them more susceptible to cancer development. This effect was observed in both laboratory mice and human patients.
The study showed that mice with severe lung infections were more likely to develop lung cancer and had a lower survival rate. Analysis of patient data revealed a 1.24-fold increase in lung cancer incidence among individuals previously hospitalized with COVID-19, regardless of smoking status or other health conditions [1].
Immune Cell Changes and Inflammation
The researchers discovered that severe viral lung infections alter the behavior of immune cells, specifically neutrophils and macrophages, which are normally responsible for protecting the lungs. These changes lead to inflammation and the creation of a “protumor” environment. The infections cause changes to the epithelial cells lining the lungs, and alveoli.
The Protective Power of Vaccination
Importantly, prior vaccination appears to prevent these cancer-promoting changes in the lungs. Vaccines train the immune system to effectively fight off infections, reducing the severity of illness and minimizing long-term immune system disruption [1].
Who is at Risk?
The increased cancer risk was primarily observed in patients who experienced severe COVID-19 infections. Interestingly, individuals with mild cases actually showed a slight decrease in risk. However, researchers caution that the millions of people globally who have recovered from severe respiratory illnesses may face an elevated risk of developing lung cancer in the coming years.
Dr. Jeffrey Sturek, a UVA physician-scientist involved in the project, suggests that severe respiratory viral infection should be considered a risk factor for lung cancer, similar to smoking. He proposes that patients at high risk, particularly those with a history of smoking, may benefit from closer monitoring with routine lung scans.
COVID-19 and Influenza: A Seesaw Effect
Recent data indicates a dynamic relationship between COVID-19 and influenza. From 2020 to 2023, influenza activity declined with the emergence of COVID-19, but subsequently rose as COVID-19 activity decreased. During the Omicron variant period, the two diseases appeared to alternate in dominance, with each lasting approximately 3 to 4 months [2]. Correlation analysis revealed a predominantly negative correlation between the two, meaning when one increased, the other tended to decrease.
Co-infection Risks
Research also highlights the increased severity of illness when influenza and SARS-CoV-2 co-infect a patient. A study in Nature demonstrated that mice infected with both influenza A virus and SARS-CoV-2 experienced significantly more severe disease and higher mortality rates than those infected with either virus alone [3]. Prior immunity to influenza, achieved through vaccination, was shown to protect against severe disease in co-infected mice [3].
Looking Ahead
These findings underscore the importance of vaccination against both COVID-19 and influenza, not only to prevent acute illness but also to potentially reduce the long-term risk of lung cancer. Researchers hope to develop targeted strategies for identifying and treating patients at higher risk of lung cancer following severe respiratory infections [1].