First Group B Streptococcal Vaccine Prevents Colonization in Healthy Nonpregnant Women

Alice Goodman

November 03, 2009

November 3, 2009 (Philadelphia, Pennsylvania) — For the first time, a Group B streptococcal vaccine was effective in preventing the spread of this infection, according to vaginal and rectal smears from nonpregnant women enrolled in a phase 3 trial. Group B streptococcus (GBS) is the most common cause of sepsis and meningitis in newborns in the United States and can cause severe illness in pregnant women, the elderly, and adults with chronic illness.

"This multicenter study was a 10-year struggle. It is a proof-of-concept study demonstrating that a vaccine can interfere with Group B streptococcus. Colonization is the single most important risk factor for invasive disease. In this study, colonization was prevented at 2 different sites. You could say it is a 2-base hit," said Sharon Hillier, PhD, from the University of Pittsburgh, Pennsylvania, who presented results at the Infectious Diseases Society of America (IDSA) 47th Annual Meeting.

Dr. Hiller said that it would be important to study such a vaccine in pregnant women; however, the particular vaccine used in this study will not be developed commercially. "It is a single vaccine directed against a single serotype of Group B streptococcus; a vaccine against a broader range of serotypes would probably have an even greater effect. We will need new commercial partners to move forward," she said.

The double-blind randomized trial consisted of 650 sexually active, healthy, nonpregnant women between 18 and 40 years who were GBS-negative in the vagina and rectum at the beginning of the study. Half the women were randomized to receive a control vaccine (licensed tetanus and diphtheria toxoids vaccine) and the other half to the GBS serotype III tetanus toxoid (GBS III-TT) vaccine. The women were evaluated bimonthly for GBS colonization for 18 months after vaccination.

Dr. Hillier said that the vaccine used in the trial was an older vaccine with a sterile diluent and thimerosal that was developed under a 1995 contract with the National Institutes of Health. The comparator vaccine was developed by Aventis. The intent-to-treat analysis consisted of 325 women in each group; 80% were between 18 and 30 years, about one third were African American, and 60% were white.

Both vaccines had comparable safety and were well tolerated. The symptoms associated with adverse events were less severe in the group vaccinated with the GBS III-TT vaccine. The most commonly reported adverse events were injection-site tenderness (87%) and pain (60%). The GBS III-TT vaccine led to a significantly longer time to acquire the first GBS-positive swab in the vagina, with an efficacy of 36% (P = .044); efficacy in the rectum was 43% (P = .015). A significantly greater proportion of women assigned to the GBS III-TT vaccine than to the comparator vaccine had cultures that were persistently negative (P = .046) Dr. Hillier said that these percentages reflected modest efficacy.

"We were pleasantly surprised by the findings for the rectal colonization. This has not been reported for any other vaccine," Dr. Hillier said.

Results With GBS Vaccine Called "Major"

GBS is a leading cause of illness in neonates and in the postpartum mother, explained Paul G. Auwaerter, MD, IDSA program chair and clinical director of the Division of Infectious Diseases at Johns Hopkins University School of Medicine in Baltimore, Maryland.

"This phase 3 trial shows that the GBS III-TT vaccine is safe, which is encouraging, since this is a significant public health problem. It is a major finding that in healthy nonpregnant women, the vaccine reduced colonization with GBS in the vaginal and rectal area," he said.

Dr. Hillier reports financial ties with Johnson & Johnson and Merck. Dr. Auwaerter has disclosed no relevant financial relationships.

Infectious Diseases Society of America (IDSA) 47th Annual Meeting: Abstract 186. Presented October 30, 2009.

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