9 years of school H. pylori screening cut teen infection rates by two thirds

If gastric cancer runs in your family, or you have ever tested positive for H. pylori (Helicobacter pylori, a spiral-shaped stomach bacterium), you have probably wondered how much difference catching it early actually makes. A new nine-year study out of Kyoto, Japan gives one of the clearest answers yet: a school-based program that tested more than 50,000 teenagers for the infection and treated everyone who tested positive, tracking exactly how much the problem shrank, and how hard it got to keep teens showing up for treatment as the stakes started to feel less urgent.

Key takeaways

• A Kyoto school screening program tested 50,031 first-year high school students for H. pylori over nine years (2015 to 2023), and the confirmed infection rate fell from 4.7% to 1.5%.
• Treatment success jumped from 76.5% with the original antibiotic combination to over 96% once the regimen was switched and a probiotic was added.
• The real vulnerability turned out to be follow-through: the share of infected teens who actually went to a doctor for treatment fell to just 15.8% by 2023.
• The ultimate goal, fewer stomach cancer cases decades from now, cannot be confirmed for another 20 to 30 years; this is a nine-year interim look at infection and treatment trends only.

Kyoto's decade-long H. pylori screening program cut teen infection rates in half

A prospective screen-and-treat program run across Kyoto Prefecture tested first-year high school students, generally 15 to 16 years old, for H. pylori every year from 2015 through 2023, and drove the confirmed infection rate down from 4.7% at the start to 1.5% by the final year. The program, published in the journal Helicobacter, targeted 50,031 students in total, offering free testing and treatment through participating schools rather than waiting for teens to seek care on their own. It is one of the largest and longest-running adolescent H. pylori initiatives reported to date, and the decline it recorded lines up with smaller programs elsewhere in Japan that found similar downward trends over shorter windows.

Why a stomach infection acquired in childhood is a decades-long cancer risk

H. pylori is the leading known cause of gastric cancer, and it is usually picked up before age five, then left untreated for years while it slowly damages the stomach lining. Left in place, the bacterium drives chronic inflammation that can progress into gastric mucosal atrophy (thinning and scarring of the stomach lining) and eventually intestinal metaplasia (a precancerous change in the stomach's cell type), both of which are difficult or impossible to fully reverse once established. That progression is why timing matters so much: a meta-analysis of cohort studies published in JNCI found that eradicating H. pylori in adults still meaningfully lowers gastric cancer risk, but the protection is incomplete precisely because the damage often has a head start by the time adults get tested. Catching and treating the infection at 15 or 16, before that damage sets in, is the entire premise the Kyoto program was built to test. H. pylori is formally classified as a known human carcinogen, and it is estimated to be behind roughly 780,000 cancer cases worldwide each year, mostly non-cardia stomach cancer, according to the National Toxicology Program's Report on Carcinogens.

A two-step test built to run inside a routine school health checkup

Students were screened using a simple urine antibody test administered alongside Kyoto's existing mandatory school health checkups, keeping the process low-friction and non-invasive. Anyone who tested positive on the urine test then took a more specific stool antigen test to confirm the result before being referred for treatment, a two-step design meant to avoid over-treating false positives from the less specific urine screen. Consent rates for participation ranged from 59.9% to 83.9% across the nine years, dipping in the middle years before recovering to around 81% by 2023. Confirmed positive students who completed treatment were checked again with a follow-up stool test at least eight weeks later to verify the infection was actually gone, not just symptomatically quieter.

What changed for teens who tested positive, and what it means if you're weighing your own testing options

For a teenager (or a parent) in this program, testing positive meant a short course of antibiotics rather than years of unmonitored risk, and the study's numbers back up how effective that course became: treatment success rose from 76.5% in 2015 to above 93% in 2016 and eventually topped 96% in later years. The researchers switched the antibiotic combination early on, from one built around clarithromycin to one built around metronidazole, after recognizing that clarithromycin resistance is unusually common in Japanese adolescents; other studies have measured resistance rates as high as 36% in Japanese children, which helps explain why the original regimen underperformed. If you are an adult and have never been tested, this study is not a reason to self-diagnose or self-treat, but it is a reasonable prompt to ask a doctor whether testing makes sense, particularly if you have a family history of gastric cancer or unexplained digestive symptoms. No specific supplement or over-the-counter product replaces a proper antibiotic course here; the probiotic strain used in this study, Clostridium butyricum MIYAIRI 588 (CBM588), was added as a supporting therapy prescribed alongside antibiotics under medical supervision, not as a standalone treatment.

The real weak point wasn't the science, it was getting teens to the doctor

The most important limitation in this study has nothing to do with the test or the antibiotics: it is how few infected students actually followed through and saw a doctor. The consultation rate among confirmed-positive students started at 84.6% in 2015 but fell to just 15.8% by 2023, with only a temporary rebound to 65.9% in 2019. The researchers could not fully explain that dip, though they point to plausible factors like embarrassment over collecting urine and stool samples, the disappearance of urgency once infection rates in the population dropped, and reduced public funding after 2022. This mirrors a pattern seen in other screening programs: follow-through on secondary testing after a positive prostate cancer screen in China runs 60% to 80%, and follow-through on colonoscopy after a positive colon cancer stool test in Japan runs only 58% to 74%, according to prior research the study authors cite. It is also worth being direct about the study's biggest unanswered question: the actual goal, fewer gastric cancer diagnoses decades from now, cannot be measured yet. The researchers themselves note that confirming a drop in cancer incidence requires 30 to 40 years of follow-up, so this nine-year report only covers infection and treatment trends, not the cancer outcomes those trends are meant to eventually prevent.

Where the program goes from here

The researchers argue the program should continue even now that infection rates have dropped below 2%, since eliminating the bacterium at 15 or 16 still heads off decades of silent inflammation before it can cause irreversible damage. Their proposed fixes for the compliance problem include automated notification systems, more direct health education delivered through school nurses, and streamlined referral pathways to reduce the friction of turning a positive test into an actual doctor's visit. They also flag non-invasive stool-based resistance testing as a future tool that could let clinicians pick the right antibiotic combination up front, rather than needing to already know a particular regimen underperforms in a given population. Funding is a live constraint: after Kyoto Prefecture covered the program's costs through 2022, it has continued on a private donation, with recruitment officially closed as of 2023.

Common Questions

What is H. pylori, and how common is it? H. pylori is a bacterium that infects the stomach lining, usually acquired in early childhood, and it is the leading known cause of stomach cancer worldwide. Infection rates vary widely by country and are generally higher where it spreads more easily through close childhood contact.

Does this study mean I should get tested? This program targeted a specific adolescent population in Japan with locally tailored testing and treatment protocols. It is not a general recommendation, but it is a reasonable reason to bring up testing with a doctor, especially with a family history of gastric cancer or persistent stomach symptoms.

Is the probiotic CBM588 something I could take on my own? No. In this study it was used as a prescribed add-on to a specific antibiotic regimen under medical supervision, not as a standalone treatment, and the study did not test it as an independent intervention.

References

1. Osamu Handa, Kazuhiko Uchiyama, Tomohisa Takagi, Yuji Naito (2026). A Decade of Screening and Treating Helicobacter pylori Infection Among First‐Year High School Students in Kyoto, Japan: Annual Trends in Infection, Consultation, and Eradication Success Rates (2015–2023). Helicobacter. https://doi.org/10.1111/hel.70156
2. Eva Doorakkers, Jesper Lagergren, Lars Engstrand, Nele Brusselaers (2016). Eradication ofHelicobacter pyloriand Gastric Cancer: A Systematic Review and Meta-analysis of Cohort Studies. Journal of the National Cancer Institute. https://doi.org/10.1093/jnci/djw132
3. Helicobacter pylori (Chronic Infection) – 15th Report on Carcinogens (NIH/NTP). NIH. https://www.ncbi.nlm.nih.gov/books/NBK590949/
4. Seiichi Kato, Shigeru Fujimura (2010). Primary antimicrobial resistance of Helicobacter pylori in children during the past 9 years. Pediatrics International. https://doi.org/10.1111/j.1442-200x.2009.02915.x