Scientists also discovered that being vaccinated against Covid and flu could help lower the risk of lung cancer in mice (Image: Getty)
Individuals who have contracted Covid could be at an increased risk of developing a certain type of cancer, as per a recent study. The research indicates that those who suffered from severe Covid-19 had a 24 per cent higher risk of developing the disease.
Researchers found the heightened risk of contracting lung cancer remained even after accounting for smoking and other known risk factors. Scientists also discovered that being vaccinated against Covid and flu could help reduce the risk of contracting the disease in mice.
As part of the study, which was published in the journal Cell, researchers examined health records from nearly 76 million American adults. Through this, they discovered that people hospitalised with severe COVID-19 had approximately a 24 per cent higher risk of subsequently developing lung cancer compared to individuals who had never been infected.
To further explore the potential link between Covid and lung cancer, the researchers infected mice with either SARS-CoV-2 or influenza A. They allowed them to fully recover, and then introduced lung tumour cells.
As reported by Study Finds, animals previously infected consistently developed larger, faster-growing tumours and died earlier than mice that had never been infected. The pro-tumour effect from influenza was still evident four months after the initial infection, reports the Mirror.
People hospitalised with severe COVID-19 had roughly a 24 per cent higher risk of subsequently developing lung cancer compared to people who had never been infected (Image: Getty)
Using a technique that identifies which DNA regions are switched on or off, the researchers found that severe respiratory infections caused enduring changes in various lung cell types, including immune cells, structural cells, and the cells lining the airways. These alterations resulted in the lungs continuing to overproduce a protein known as G-CSF long after recovery.
G-CSF is a signal that draws in neutrophils, white blood cells that normally arrive during an infection, carry out their role, and then depart. In the lung following a viral infection, a particular group of neutrophils accumulated in substantial numbers and stayed.
Rather than protecting the host, they blocked anti-tumour immune responses and encouraged tumour cell growth.
In a further test, mice that received a SARS-CoV-2 mRNA spike vaccine before virus exposure were fully protected from severe illness. When these vaccinated animals were subsequently exposed to tumour cells, they displayed markedly lower tumour loads than unvaccinated animals that had undergone complete infection.
A comparable experiment using an inactivated influenza vaccine produced the same result.
The severity of infection proved significant even amongst unvaccinated animals. Mice given small amounts of either virus, enough to trigger only mild illness, did not show a notable increase in tumour burden.
It was serious infection, the kind involving significant lung inflammation, which triggered the reprogramming. Vaccines, within these studies, appeared to prevent not only the immediate illness but also the cancer-related effects that emerged afterwards.
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.”
However, it is important to note that there are limitations to this study. The human data in this study is retrospective, meaning researchers examined existing health records rather than following patients prospectively in a controlled trial.
It also cannot be ruled out that people who developed severe Covid-19 may have already had undetected precancerous changes that contributed both to disease severity and to subsequent cancer diagnosis.