OM-89 for Repeat UTIs: What a 34% Reduction Means

OM-89, also called Uro-Vaxom, is an oral bacterial extract studied for preventing recurring urinary tract infections. A frequently cited benefit comes from a study published in 2005. Its numbers describe two different outcomes, and both deserve to keep their original meaning.¹²

The 2005 study counted infections over a year

The double-blind, placebo-controlled study treated 453 women: 231 with OM-89 and 222 with placebo. The research schedule used a daily capsule for 90 days, three months without treatment, then ten-day courses in months 7, 8 and 9. Follow-up lasted 12 months.¹

Average post-enrollment UTI counts were 0.84 with OM-89 versus 1.28 with placebo. The authors reported a 34% relative reduction. Subtracting the averages gives 0.44 fewer episodes per woman during follow-up. Neither figure tells us how many individual women avoided every infection.¹

The paper reported that separately: 40.3% of OM-89 recipients and 55.0% of placebo recipients had at least one further UTI. That is a 14.7-percentage-point difference, calculated from the reported proportions. It is a different measure from the relative reduction in average episode counts.¹

Those are study results under a particular treatment and follow-up schedule, rather than a guaranteed reduction for someone considering the product today.

A later trial tested a modified preparation

A 2015 randomized trial³ enrolled 451 women and tested OM-89S, made using a modified process for breaking down the bacteria. In its first period, three months of treatment were followed by three months of observation. Mean UTI counts were 0.66 with OM-89S and 0.63 with placebo, with no significant difference (P = 0.95).³

The researchers identified several possible limitations: fewer infections than expected, major protocol violations in 188 participants (41.7%) and the manufacturing change. The study did not establish which factor explained the result. It should not be described as an exact replication using an unchanged preparation.³

Two authors disclosed employment with Vifor Pharma; other authors disclosed research or consulting relationships, including with OM Pharma.³

The newer pooled result still carries uncertainty

A 2025 meta-analysis combined eight trials with 1,351 participants. It reported lower odds of symptomatic UTI with treatment (odds ratio 0.48; 95% confidence interval 0.23 to 0.97), with substantial variation between studies (I² = 81%). An odds ratio is not a percentage of people protected.²

The pool included OM-89S and studies involving neurogenic bladder dysfunction, so it was not a single uniform population of otherwise healthy women taking one unchanged preparation. Its analysis also found smaller apparent benefits in newer studies. That study-level trend cannot establish why results changed or prove that a particular patient’s response weakens over time.²

A pooled estimate can summarize the studies while leaving a clinician uncertain about how well it applies to you.

Put those numbers beside current guidance

The European Association of Urology’s⁴ current online guideline gives a weak recommendation for immunomodulatory prevention of recurrent cystitis in a regulated clinical trial. Its discussion describes low-certainty evidence and differences between the preparations. This is narrower than a recommendation for routine use of every product described as a UTI vaccine.⁴

The guideline also recommends confirming recurrent cystitis with urine culture. Bring dates of symptomatic episodes, culture results when available, treatments received and how soon symptoms returned. That record helps distinguish repeated confirmed infections from symptoms that need another explanation.⁴

For a prevention appointment, ask:

• Which episodes support the diagnosis of recurrent infection?
• Does the proposed product match the preparation studied, and is it authorized or supplied through a trial here?
• What alternatives fit my history, and how will we judge whether prevention is helping?

A prevention discussion should not delay assessment of new illness. NHS⁵ guidance advises urgent assessment for a suspected UTI with temperature changes, shivering or back pain just under the ribs. These can be signs of a kidney infection.⁵

Laugh, Sneeze, Jump, Chapter 3’s “How to Use This Book With a Professional,” discusses preparing a history and questions before an appointment. Use that approach to organize the conversation; the chapter does not prescribe OM-89 or determine which prevention option suits you.