New research from the University of Virginia (UVA) links severe respiratory viral infections that require hospitalization to a later rise in lung cancer diagnoses, but also shows vaccination can largely block the immune changes behind that increased risk. The effect was specific to severe COVID-19 or influenza cases: the study reports a 1.24-fold (24%) higher lung cancer incidence in hospitalized patients, while mild COVID-19 cases did not show this increase.
How the risk showed up in people and what the 1.24-fold number means
Using health records, UVA researchers compared groups by infection severity and found that hospitalization for COVID-19 or flu correlated with a roughly 24% higher chance of receiving a lung cancer diagnosis months to years later, after adjusting for smoking and other comorbidities. The team emphasized that this association was strongest among those whose infections required hospital care — the elevated risk did not extend to mild outpatient COVID-19, and some analyses even suggested a slightly lower cancer incidence in mild cases.
That 1.24-fold figure is an adjusted relative increase, not an absolute probability. For an individual it changes baseline risk by a proportional amount; for clinicians and public-health planners it flags a new, nontraditional exposure (severe viral pneumonia) to consider alongside smoking, age, and prior lung disease when deciding surveillance intensity.
What happened in the lungs: immune reprogramming seen in mice and tissue studies
Laboratory work accompanying the human data showed a plausible mechanism. In mouse models of severe SARS-CoV-2 and influenza pneumonia, neutrophils and macrophages — immune cells that normally resolve infection — adopted persistent, pro-inflammatory states that altered lung epithelial cells and created an environment permissive to tumor growth. Those mice developed more lung tumors and had higher mortality from lung cancer compared with controls.
Those cellular changes provide a causal bridge: severe infection appears to reprogram innate immune cells in ways that sustain low-grade inflammation and tissue remodeling, a known promoter of carcinogenesis. UVA investigators used this combination of human epidemiology plus mouse experiments to argue the relationship is not just correlation but biologically plausible causation.
Practical implications: vaccination, screening thresholds, and who should act first
Vaccination emerged as a practical countermeasure in the study: vaccinated animals and vaccinated human cohorts showed reduced severity of infection and a lower incidence of the immune alterations associated with tumor promotion. That suggests a two-part prevention logic for clinicians and patients: reduce the risk of severe infection (vaccines, early antivirals such as Paxlovid for COVID-19 or oseltamivir/Tamiflu for influenza) and consider tailoring post-infection surveillance based on severity and baseline risk factors.
UVA researchers recommend clinicians consider enhanced lung-cancer surveillance — for example, routine low-dose chest CT — for people who were hospitalized with viral pneumonia, especially current or former smokers and those with chronic lung disease. The recommendation is conditional, not universal: thresholds that make sense today are hospitalization plus at least one other risk factor (age, smoking history, prior COPD), pending guideline updates.
Limits, watchpoints, and immediate decision checkpoints
Important caveats remain. Some hospitalized patients may already have had undiagnosed lung cancer or pre-existing lung pathology that contributed both to severe infection and later cancer detection; the study acknowledges this potential confounding. Researchers also note incomplete clarity on how prior vaccination status in the human cohorts affected long-term cancer outcomes, so further stratified analyses are needed before changing screening rules broadly.
| Clinical scenario | Observed change in lung cancer risk | Practical next step |
|---|---|---|
| Hospitalized for COVID-19 or influenza | ~1.24-fold higher incidence (adjusted) | Discuss low-dose chest CT surveillance if age/smoking history or chronic lung disease present |
| Mild, outpatient COVID-19 | No increase; some data suggest slight reduction | Routine follow-up per existing screening guidelines; prioritize vaccination |
| Vaccinated before infection | Lower likelihood of severe immune reprogramming in study models | Vaccination remains a primary preventive measure to reduce long-term risk |
Quick Q&A
Who should ask for extra lung screening now? Patients hospitalized with viral pneumonia who are older, current/former smokers, or have chronic lung disease should discuss earlier CT screening with their clinician.
Does a mild COVID-19 infection raise my lung cancer risk? No — the reported increase is specific to severe, hospitalized infections; mild outpatient COVID-19 did not show the risk rise in the study.
Can vaccination change this long-term risk? The UVA data and accompanying mouse experiments indicate vaccination reduces infection severity and blocks the harmful immune changes, making vaccination a pragmatic step to lower this pathway to cancer.