New Lancet study links 12% of global cancer cases to 12 infectious diseases

For most such infections, there are vaccines or vaccines in development

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Let's add preventable cancers to this list

The worldwide incidence analysis, conducted by epidemiologists at the World Health Organization’s International Agency for Research on Cancer (IARC), evaluated 12 infectious agents classified as Group 1 human carcinogens. 

The findings demonstrate that roughly 1 in every 8 cancers diagnosed globally is linked to an underlying infection, representing a substantial cancer burden that could be prevented or mitigated using existing vaccines, diagnostic screenings, and antimicrobial therapies.

The global proportion of infection-attributable cancers has remained essentially unchanged since the agency's previous assessment in 2018 (which estimated 13%), highlighting persistent gaps in worldwide vaccination uptake, screening infrastructure, and therapeutic access.

The 12 Pathogens: Which Infections Cause Cancer?

The vast majority of infection-driven cancers in 2024 were concentrated among five primary pathogens, with two leading agents responsible for more than 1.5 million cases:

• Helicobacter pylori (760,000 cases / 4% of all global cancers): A common bacterium that colonizes the stomach lining, typically transmitted through contaminated food, water, or poor hygiene. It is the leading cause of non-cardia gastric cancer (accounting for 700,000 cases, or 85% of all non-cardia stomach cancers) and causes cardia gastric cancer (42,000 cases) and gastric non-Hodgkin lymphoma (18,000 cases).
• Human Papillomavirus / HPV (750,000 cases / 4% of all cancers): The primary driver of cervical cancer, which accounted for 600,000 cases (100% attributable to HPV). HPV is also responsible for 58,000 cases of oropharyngeal, tonsil, and base-of-tongue cancers, 32,000 anal squamous cell carcinomas, 18,000 penile cancers, 14,000 vaginal cancers, and 12,000 vulvar cancers.
• Hepatitis B Virus / HBV (360,000 cases / 2% of all cancers): Contracted through blood, sexual contact, contaminated needles, and perinatal transmission from mother to child. It accounts for 330,000 cases of hepatocellular carcinoma (primary liver cancer) and 27,000 cases of intrahepatic cholangiocarcinoma.
• Epstein-Barr Virus / EBV (260,000 cases / 1% of all cancers): A ubiquitous herpesvirus carried by more than 90% of adults. It was linked to 110,000 cases of nasopharyngeal carcinoma, 78,000 cases of gastric adenocarcinoma, 47,000 cases of Hodgkin lymphoma, 20,000 cases of diffuse large B-cell lymphoma, and 6,200 cases of Burkitt lymphoma.
• Hepatitis C Virus / HCV (160,000 cases): A bloodborne virus causing chronic hepatitis, responsible for 130,000 cases of hepatocellular carcinoma, 17,000 cases of non-Hodgkin lymphoma, and 11,000 cases of intrahepatic cholangiocarcinoma.
• Kaposi's Sarcoma-Associated Herpesvirus / KSHV (35,000 cases): Responsible for 34,000 cases of Kaposi's sarcoma and rare primary effusion lymphomas.
• Other Classified Infectious Agents (19,000 cases combined): Human T-cell lymphotropic virus type 1 (HTLV-1, causing 3,900 cases of adult T-cell leukaemia/lymphoma); Schistosoma haematobium (a parasitic waterborne flatworm causing 5,900 bladder squamous cell carcinomas); liver flukes Opisthorchis viverrini and Clonorchis sinensis (causing 3,800 bile duct cancers); Merkel cell polyomavirus (causing 3,200 aggressive Merkel cell skin carcinomas); and HIV (which directly caused 2,300 cases of conjunctival eye cancer and contributed via immunosuppression to tens of thousands of HPV- and KSHV-related cancers).

Biological Mechanisms: How Microbes Trigger Malignancy

Most people infected with these pathogens never develop cancer, and malignancies often take decades to emerge. However, the study outlines several distinct biological pathways through which persistent infections initiate carcinogenesis:

• Disruption of Cellular Growth: Viruses such as EBV and HPV integrate genetic material or viral oncoproteins into host cells, interfering with tumor suppressor proteins (such as p53 and retinoblastoma protein) and driving uncontrolled cell proliferation.
• Chronic Tissue Inflammation: Pathogens like H. pylori, Hepatitis B, and Hepatitis C cause decades of chronic localized inflammation, resulting in continuous cellular turnover, oxidative DNA damage, and tissue scarring (such as liver cirrhosis or gastric atrophy) that elevates mutation risks.
• Immune System Suppression: HIV directly targets and degrades immune surveillance, preventing the body from detecting abnormal cells and allowing other opportunistic oncogenic viruses (such as KSHV and HPV) to replicate unimpeded.

Global Inequities: Where the Burden Falls Heaviest

The study revealed stark geographical and economic disparities, with low- and middle-income nations bearing 77% of all infection-attributable cancer diagnoses:

• Eastern Asia: Holds the largest regional share worldwide, accounting for 990,000 cases (42% of the global total) with an age-standardized incidence rate of 31.9 per 100,000 person-years. This concentration is heavily driven by H. pylori stomach cancers and HBV liver cancers across China, South Korea, Japan, and Mongolia.
• Sub-Saharan Africa: Recorded the highest proportional burden for HPV, where 14% of all cancer diagnoses were HPV-driven (130,000 cases), alongside elevated rates of KSHV-related Kaposi's sarcoma.
• Western & High-Income Nations: Exhibited significantly lower overall infection-related cancer proportions (ranging from 4% in Northern Europe to 5% in North America), though North America showed higher incidence rates for Hepatitis C-related liver cancer (2.2 per 100,000) than the global average.

How to Reduce Risk: Proven Tools and Future Vaccines

Public health specialists and oncologists emphasize that unlike many genetic cancer risks, infection-related cancers can largely be prevented, diagnosed early, or cured using accessible clinical tools:

• Immunization: The Hepatitis B vaccine—the first vaccine developed against cancer—is administered in a three-dose infant series starting within 24 hours of birth to provide lifelong liver cancer protection. The HPV vaccine, recommended between ages 9 and 12, provides near-complete protection against the high-risk viral strains (primarily HPV 16 and 18) responsible for cervical and oropharyngeal cancers.
• Bacterial Eradication: Simple non-invasive breath or stool antigen tests can detect active Helicobacter pylori infections, which can be cured with a short course of targeted antibiotics and proton-pump inhibitors, sharply lowering long-term gastric cancer risk.
• Antiviral Cures and Prophylaxis: Direct-acting antiviral (DAA) medications can eliminate Hepatitis C in over 95% of patients within 8 to 12 weeks. For HIV, consistent antiretroviral therapy (ART) and pre-exposure prophylaxis (PrEP), combined with barrier contraception, preserve immune function and prevent coinfection-driven malignancies.
• Routine Precancer Screening: Pap smears and HPV DNA testing detect abnormal cervical cells before they progress to invasive cancer, while endoscopic screening in high-risk East Asian populations catches early-stage gastric lesions.
• Vaccine Pipeline for EBV: While no approved vaccine currently exists for Epstein-Barr virus, recent clinical interest—driven by links to both cancer and multiple sclerosis—has pushed several candidate EBV vaccines into human clinical trials.