Scientists have revealed how people who had previously had Covid-19 have a heightened risk of one particular kind of cancer.
Although the worst of the coronavirus pandemic is behind us and restrictions have long since lifted, researchers say its effects are still being uncovered.
A major focus has been the lasting health issues that can follow infection, with scientists continuing to investigate what Covid-19 might trigger in the months and years afterwards.
Now, a new study has reported an association between a past Covid-19 infection and increased odds of developing a specific cancer.
Because Covid primarily targets the respiratory system, severe illness can lead to serious breathing difficulties and inflammation in the lungs.
To explore potential long-term outcomes, researchers analysed health records from around 76 million people and identified a striking pattern.
The team found that people who had Covid-19—particularly those with more serious illness—appeared more likely to develop lung cancer than those who were never infected or only experienced mild symptoms.
Researchers also reported that the link persisted even after taking smoking into account, which is one of the most significant contributors to lung cancer risk.
In other words, traditional risk factors such as smoking did not fully explain the increased likelihood seen among those who had experienced Covid-19.
The study estimated that a severe Covid-19 illness was associated with roughly a 24 percent increase in lung cancer risk.
The authors also suggested vaccination could help reduce this effect, referencing findings from experiments conducted in mice.
The research was published in the journal Cell and focused on patient data from the United States.
According to the study, the increased risk was most evident among people who had been hospitalised with Covid-19.
In addition to the human data, scientists ran animal studies in which mice were infected with either SARS-CoV-2 or influenza A and then allowed to fully recover.
Once the mice recovered, the researchers introduced lung tumour cells and monitored how the cancers developed.
They observed that mice previously infected with Covid developed larger tumours that progressed more rapidly than those in mice that had not been infected.
As a result, the Covid-infected mice also died sooner than the animals in the comparison group.
The researchers further reported that the cancer-promoting effect linked with Covid infection appeared to remain for months, with signs it was still present around four months after the initial infection.
The study authors wrote: “The Covid-19 pandemic has highlighted the long-term consequences of viral pneumonia, yet its impact on cancer development remains unclear. Here, we show that patients previously hospitalised with severe Covid-19 have an increased risk of subsequent lung cancer.
“Across multiple murine models, severe respiratory viral infections accelerated lung cancer growth, whereas vaccination mitigated infection-enhanced tumour progression.”