Infections may be responsible for one in every eight cancer cases worldwide, with vaccination and other preventive measures capable of stopping many of them, according to new research.
A study by researchers at the International Agency for Research on Cancer found that roughly 2.3 million of the 19.2 million new cancer cases recorded globally in 2024 were associated with infections.
Five infections accounted for the overwhelming majority of those cases.
They were Helicobacter pylori, or H. pylori, a widespread stomach bacterium commonly transmitted through contaminated food or water; human papillomavirus (HPV); hepatitis B and C; and Epstein-Barr virus (EBV), the infection best known for causing glandular fever.
Low- and middle-income countries carried the heaviest burden, recording about 77 per cent of all cancer cases linked to infection.
Eastern Asia reported the highest regional total, with 990,000 infection-related cancer cases—42 per cent of the worldwide figure. H. pylori and hepatitis B were the main drivers.
Writing in The Lancet Oncology, the researchers said the findings underline how stronger infection prevention and control could help reduce cancer rates.
“Although investment in the development of new preventive vaccinations is key, many prevention strategies are known to be cost-effective,” the authors wrote.
Infections may contribute to one in eight cancers worldwide, many of which could be prevented with vaccination
“Unfortunately, such strategies are often underused due to societal, financial and political barriers, often in the settings that need them most.”
The researchers highlighted several practical measures, including improving HPV vaccine uptake, encouraging safer injection practices, expanding access to condoms and HIV prevention medication such as PrEP, and detecting and treating early cervical and anal cancers.
In Western Europe, HPV was associated with 24,000 cancer cases in 2024, making it the region’s leading infection-related cause of cancer.
HPV is a common virus that affects the skin and the cells lining areas inside the body, including the mouth, throat and genitals.
It is usually transmitted through close skin-to-skin contact during sexual activity. For most people, however, the virus causes no health problems.
Around 14 high-risk HPV types can raise the likelihood of cancer. Over time, they can alter the DNA within cells, prompting uncontrolled growth that may develop into cancer.
HPV causes nearly all cervical cancer cases and is also associated with cancers affecting the throat, mouth, anus, penis, vulva and vagina.
For that reason, the researchers said HPV vaccination and cervical screening form the foundation of the World Health Organisation’s plan to eliminate cervical cancer.
H. pylori bacteria live within the protective mucus lining the stomach
In the UK, cervical screening is available to all women aged between 25 and 64.
The HPV vaccine is routinely offered to children aged 12 and 13 and can significantly lower the risk of developing cancers linked to the virus.
It is also available to people up to the age of 25 who missed the jab at school, as well as men who have sex with other men up to the age of 45.
Using condoms can also help reduce the risk of infection.
The study found that H. pylori was the single biggest infection-related cause of cancer worldwide in 2024, accounting for around 760,000 cases.
Most were stomach cancers, with several European countries now screening people for the bacterium.
Research published earlier this month suggested H. pylori may also be responsible for up to one in five bowel cancer cases – with those exposed to the bacteria facing a 60 per cent increased risk of colorectal cancers than those who have never been exposed.
However, the researchers noted that progress in developing vaccines against H. pylori has been slow, despite experts saying such advances could have a major impact on reducing stomach cancer rates worldwide.
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Meanwhile, Epstein-Barr virus – which infects around 95 per cent of UK adults at some point in their lifetime – now ranks as the fourth-largest cause of cancer globally, ahead of hepatitis C.
Experts said the finding was concerning given how widespread the virus is.
However, the researchers stressed that infection alone is unlikely to cause cancer, with factors such as genetics, overall health and diet also thought to influence risk.
The team concluded: ‘As there are currently no efficient strategies to control infection, EBV should be considered an important target for prevention.’
Several clinical trials looking into EBV vaccines are ongoing.
Hepatitis B and C combined accounted for around a third of all infection-related cancers, most of which were liver cancer.
Unlike many other cancer risk factors, researchers said hepatitis-related cancers should be highly preventable, because effective treatments already exist.
Hepatitis B can also now be controlled with antiviral drugs, while hepatitis C can now be cured in most patients.
In the UK, the NHS recommends hepatitis B vaccination for all babies as part of the routine childhood vaccination and high-risk individuals including those who inject drugs, men who have sex with men, sex workers, people with chronic liver disease or kidney failure and healthcare workers.
There is currently no approved vaccine for hepatitis C. The virus spreads through contact with infected blood and prevention relies on testing, treatment and reducing exposure.
The NHS advises people not to share toothbrushes or razors, to ensure tattoos and piercings are carried out by licensed providers and to practise safer sex to limit the risk of infection.
The findings come amid growing concern that modern lifestyles may be fuelling an epidemic in early-onset cancer – before the age of 50 – especially in women.
The Government’s long-awaited national cancer plan is expected to include measures to improve lifestyles, diagnose and treat patients earlier, and to help people with cancer remain in or get back to work.