Objectives: Recurrent urinary tract infections (R-UTIs) are very common amongst women, and alternatives to antibacterial prophylaxis are necessary. This study evaluates the effectiveness of a sublingual bacterial vaccine for the prophylaxis of R-UTIs. Methods: We conducted a quasi-experimental pretest-posttest study of 166 women diagnosed with R-UTIs. Both before and after the start of treatment with the vaccine, we analysed the total number of R-UTI episodes, the urine culture results, and the type and number of antibiotic packages consumed. Symptoms and urine cultures were evaluated 3, 6, 9, 12, 18, and 24 months after initiating treatment with the vaccine. Results: The mean time of follow-up after vaccination was 1.7 years. After vaccination, there was a 54.6% reduction in episodes of UTI, and a 56.2% reduction in positive urine cultures. At 3 months, 74.4% of the patients had no R-UTI, the rate falling to 68.1% at 6 months, 52.4% at 12 months, and 44.5% at 24 months. The cumulative probability of maintaining negative urine cultures was 76% at 3 months, 37% at 12 months, and 18% at 2 years. Conclusions: The use of a sublingual bacterial vaccine for the prophylaxis of R-UTIs in women is an effective treatment that contributes to a reduction in the number of UTI episodes.