Vaccine prevents urinary-tract infections. (Science News of the week).

Infections of the urinary tract that plague many young women may someday be avoidable, researchers report. An experimental vaccine designed to repel 10 common bacteria that cause these problems, also known as bladder infections, has cleared a key hurdle by proving safe and effective in a group of women.

By packaging heat-inactivated versions of the 10 bacteria into a vaginal suppository, scientists developed a vaccine that could not only spare women these recurring irritations but also prevent the scarring and other damage they can cause to the kidneys. The bacterial roster includes six strains of Escherichia coli and four other species.

First developed in an injectable form by the Swiss firm Solco, the experimental vaccine is now being produced as a suppository by Cincinnati-based Protein Express. To test its safety and potential effectiveness, immunologist Walter J. Hopkins and his colleagues at the University of Wisconsin-Madison identified 54 women who had had at least 3 urinary-tract infections--and as many as 20--in the previous year.

The researchers randomly assigned one-third of the women to receive six inert suppositories over 14 weeks. Another third of the group was given the same number of vaccine suppositories, while the remaining women received first three vaccine suppositories and then three placebo suppositories.

Only 8 of the 18 women getting the full course of vaccine had any urinary-tract infection during the 6-month study, compared with 16 of 18 women in the placebo group. The women getting a partial dose fended off infections while they used the vaccine suppositories, but this protection faded when they switched to the placebos. Hopkins presented the findings in Chicago last month at the Interscience Conference on Antimicrobial Agents and Chemotherapy.

Because the vaccine directly contacts the lining of the vagina, the researchers suggest that it elicits antibodies that target mucosal tissue there and repel microbes. The antimicrobial response also may include other immune proteins and cells, Hopkins says.

Preventing urinary-tract infections without resorting to antibiotics would represent "a striking advantage" for doctors and patients in fighting this condition, says David C. Hooper, a physician at Massachusetts General Hospital in Boston. Many bacteria, including those used to make this vaccine, have become resistant to certain antibiotics. A reliable vaccine would prevent bacteria from infecting a person and simultaneously help public health officials by limiting antibiotic use, which can lead to drug resistance, Hooper says.

Hopkins and his colleagues are planning a large, multiclinic trial with hundreds of participants. The Food and Drug Administration typically requires such studies before it will approve a new drug or vaccine. Hopkins notes that the trial probably won't start for a year or more and will take up to 2 years to complete.