Vaccine Development for Urinary Tract Infections: Where Do We Stand?

Urinary tract infections (UTIs) are among the most common bacterial infections. Its management has become increasingly challenging due to antimicrobial resistance. The four mainstays to tackle this crisis rely on the development of new antibiotic agents, the introduction of preventive and alternative antimicrobial strategies, the concept of antimicrobial stewardship, and effective hygiene measures. One of the most effective approaches to prevent UTIs is the design of a potent vaccine. OM-89 is a lyophilised preparation of membrane proteins from 18 different uropathogenic Escherichia coli strains. The safety and efficacy of this immunoactive agent is well documented; therefore, it is recommended for the prophylaxis of UTI according to the current European Association of Urology guidelines on urological infections. In terms of a true vaccine designed to target specifically pathogenic bacteria, no substance is currently available. ExPEC4V, a novel tetravalent bioconjugate vaccine against extraintestinal pathogenic E. coli, was evaluated for safety, immunogenicity, and clinical efficacy in a randomised, single-blinded, placebo-controlled phase 1b trial. The vaccine was well tolerated and elicited a robust antibody response in patients suffering from recurrent UTIs. Although the first clinical data suggested a reduced incidence of UTIs after vaccination, especially for higher bacterial loads, further randomised controlled trials are necessary to determine its true clinical benefit.