• Explain to interested patients that group B streptococcus is a major cause of sepsis and meningitis in newborns in the U.S.
• Note that this study details early steps toward a vaccine against the pathogen.
• Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered preliminary until published in a peer-reviewed journal.

PHILADELPHIA — An investigational vaccine against a strain of group B streptococcus that causes sepsis and meningitis in newborns was safe and modestly effective, a researcher said here.

In a Phase II, double-blind, randomized trial, the vaccine against serotype III of the bacteria did a better job of preventing colonization in women than placebo, according to Sharon Hillier, PhD, of the University of Pittsburgh.

The most common adverse events were injection site tenderness and pain, Hillier reported at the annual meeting of the Infectious Diseases Society of America.

Group B streptococcus, commonly found in the gut and genital tract, can cause disease in pregnant women, the elderly, and adults with some chronic conditions.

But the reason researchers are seeking a vaccine is that when it’s transmitted during delivery, group B streptococcus is also the most common cause of sepsis and meningitis in newborns in the U.S.

The test vaccine is a combination of the bacterial polysaccharide and tetanus toxoid and was compared with a licensed tetanus and diphtheria vaccine in 650 sexually active women, nonpregnant women who were not colonized with the bacteria at baseline, Hillier said.

The women were tested bimonthly after vaccination to see if they had been colonized or infected by Group B streptococcus, she said. The primary endpoint was time to acquisition of the bacteria.

The researchers found:

• For preventing vaginal acquisition of type III Group B streptococcus, the vaccine efficacy was 35%, which was significant at P=0.044.
• For rectal acquisition, efficacy was 43%, significant at P=0.015.

Women in the vaccine group also had a robust immune response to the bacteria.

The geometric mean concentration of serum IgG to the bacteria two months after vaccination was 12.6 micrograms per milliliter, compared with 0.30 in the control group, a difference that was significant at P<0.0001, Hillier reported.

As well, 95% of women in the vaccine group — but less than 1% of the controls — responded with at least a four-fold rise in serum IgG above prevaccination levels, she said.

Antibody production rather than prevention of colonization is a more common measure of vaccine efficacy although prevention of infection is the gold standard for efficacy.

Currently, physicians screen women for group B streptococcus before delivery, according to Neil Fishman, MD, of the University of Pennsylvania, an infectious diseases specialist who was not part of the study.

If the test is positive, antibiotics are used to clear the pathogen, he said, “but this isn’t perfect, as the bacteria can be resistant to the antibiotics.”

The study is preliminary but encouraging, said Larry Pickering, MD, of Emory University in Atlanta, who was not part of the study but who moderated the session at which the data were presented.

“It’s important, in that they showed it prevented colonization,” he said. “But there’s still a lot of work to do” to get broader and more powerful protection.