1 In 8 Cancer Cases Are Caused By Infections, Underscoring The Importance Of Vaccines, Experts Say

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A study published Sept. 28 in The Lancet Oncology estimates that infections with 12 pathogens caused about 2.3 million cancer cases worldwide in 2024, or 12% of diagnoses. Four pathogens accounted for roughly 92% of those cases, while most infection-related cases occurred in low- and middle-income countries.

A global analysis published in The Lancet Oncology on Sept. 28 estimates that infections caused about 2.3 million cancer cases in 2024 — around 12% of the roughly 20 million new cases worldwide. The study links those cancers to 12 viruses, bacteria and parasites, highlighting the potential role of infection prevention, including vaccination, in reducing some cancer cases.

Researchers drew on estimates from the Global Cancer Observatory’s GLOBOCAN database, which compiles cancer-registry data, and combined them with published evidence on infections among people with particular cancers. The analysis estimated how many cases could be attributed to each of the 12 pathogens studied; it did not count every individual infection as causing cancer.

Four pathogens accounted for about 92% of the infection-attributed cases. Helicobacter pylori, a bacterium that infects the digestive tract, was linked to an estimated 760,000 cases, mainly gastric cancers. Human papillomavirus (HPV) accounted for about 750,000, including cervical, penile, throat and mouth cancers. Hepatitis B was linked to 360,000 cases, and Epstein-Barr virus (EBV) to 260,000.

The figures are estimates, rather than a direct tally of confirmed causes in each patient. The study’s broad message is that cancers associated with certain infections may be preventable by reducing infection, but the available prevention options differ by pathogen. Vaccines exist for HPV and hepatitis B; the source report says there is no approved EBV vaccine.

Prevention Could Reduce Some Cancers

The estimates point to a substantial cancer burden associated with infections, but they do not mean that every case linked to a pathogen could be prevented. They do show why vaccination and other infection-control measures matter alongside established cancer prevention approaches, screening and care.

Prevention access is uneven. The World Health Organization reported that 31% of eligible adolescent girls worldwide received at least one HPV vaccine dose in 2024, far below its 90% target. The study found that low- and middle-income countries accounted for 77% of infection-driven cancer cases; around 81% of HPV-linked cancers occurred in those countries. Those disparities mean that the benefits of prevention are not distributed evenly.

HPV and hepatitis B vaccination can prevent infections that are associated with cancers. The estimates do not quantify how many future cancer cases a particular vaccination campaign would avert, but experts cited in the source report argue that improving coverage could lower the burden over time. Other risk factors, including tobacco and alcohol use, also contribute to cancer risk and remain relevant to prevention.

Four Pathogens Drive Most Cases

The study considered 12 cancer-associated pathogens, including HPV, hepatitis B and C, HIV and EBV. Its estimates combined overall cancer data with previously published information about infection prevalence in specific cancers. This approach provides a global picture, but it relies on the quality and coverage of the underlying data.

HPV and hepatitis B have vaccines, while prevention for other infection-related cancers may depend on different public-health measures. The source report notes that HPV vaccination uptake remains below the WHO target globally. It also reports that some countries with high HPV vaccine coverage have seen cervical cancer begin to decline, citing comments from researchers and clinicians not involved in the new analysis.

Experts quoted in the report said a single-dose HPV schedule could ease delivery by reducing costs and the need to bring recipients back for another dose; the source describes this approach as supported by recent trials. That is a policy and implementation consideration, not a finding that the new global burden analysis itself tested.

“The biggest misconception from families is that the HPV vaccine is not needed or that it can wait.”

— Dr. Rebecca Perkins, an obstetrician-gynecologist at Tufts University School of Medicine, who was not involved in the study

Limits of the Global Estimates

The 2.3 million figure is an estimate based on cancer-registry data and published research on infection prevalence, not a case-by-case determination that an infection caused each cancer. The source material does not provide enough detail to assess how uncertainty varies by pathogen, country or cancer type, or how gaps in diagnostic and registry coverage may affect individual estimates.

The analysis identifies cases attributed to infections, but it does not establish how many could be prevented through vaccination or other interventions in practice. Outcomes depend on factors such as vaccine access, uptake, timing and the role of other cancer risks. The source report also gives no full breakdown for all 12 pathogens beyond the leading examples.

It is also unclear from the available material how the study’s estimates compare with earlier global estimates using the same methods. The figures should be read as the researchers’ assessment of the 2024 burden, not as a direct measure of year-to-year change.

Vaccination Access and Further Research

The immediate public-health focus identified by experts in the report is to improve access to HPV and hepatitis B vaccination, particularly in places carrying a large share of infection-associated cancers. Governments and health agencies can also weigh evidence on vaccine schedules and delivery approaches, including whether single-dose HPV programs are practical for their populations.

Researchers will need to keep refining estimates as cancer registries and evidence about infection-related cancers improve. Work on an EBV vaccine remains a separate research challenge, according to Shannon-Lowe’s comments in the source report. The study does not announce a new vaccine or policy change; the next developments will depend on public-health decisions, vaccine coverage and further research.

Key Questions

What does the study mean by 1 in 8 cancer cases?

The researchers estimate that infections caused about 2.3 million of roughly 20 million new cancer cases worldwide in 2024, or approximately 12%. It is a population-level estimate, not a claim that every infection leads to cancer.

Which infections accounted for most of the cases?

The four leading pathogens were H. pylori, HPV, hepatitis B and EBV. Together, they accounted for about 92% of the cancer cases attributed to infections in the analysis.

Can vaccines prevent infection-related cancers?

Vaccines against HPV and hepatitis B can prevent infections associated with some cancers. The analysis estimates the infection-related burden; it does not calculate exactly how many cases a specific vaccination program would prevent.

Where is the infection-related cancer burden concentrated?

The study estimates that low- and middle-income countries accounted for 77% of infection-driven cancer cases. The source report says about 81% of HPV-linked cancers occurred in those countries.

Is there an approved vaccine for Epstein-Barr virus?

The source report says there is no approved EBV vaccine. A virologist quoted in the report described the virus’s complexity as a challenge for vaccine development.

Source: fediverse