Maternal vaccine can prevent group B strep in young infants

A hexavalent capsular polysaccharide (CPS)-cross-reactive material 197 glycoconjugate vaccine (GBS6) can prevent invasive group B streptococcus in young infants, according to a study published in the July 20 issue of the New England Journal of Medicine.

Shabir A. Madhi, M.D., Ph.D., from the South African Medical Research Council Vaccines and Infectious Diseases Analytics Research Unit in Johannesburg, and colleagues conducted an ongoing phase 2, placebo-controlled trial involving pregnant women to assess the safety and immunogenicity of a single dose of various GBS6 formulations and analyzed maternally transferred anti-CPS antibodies.

In a parallel seroepidemiologic study, serotype-specific anti-CPS immunoglobulin G (IgG) concentrations that were associated with a reduced risk for invasive disease among newborns were assessed to define putative protective thresholds.

The researchers found that among infants in the seroepidemiologic study, naturally acquired anti-CPS IgG concentrations were associated with a reduced risk for disease. IgG thresholds of 0.184 to 0.827 µg/mL were determined to be associated with 75 to 95 percent reductions in the risk for disease. There were no GBS6-associated safety signals among mothers or infants.

Across the trial groups, the incidence rates of adverse events and serious adverse events were similar for mothers and infants; the groups that received GBS6 containing aluminum phosphate had more local reactions. GBS6 induced maternal antibody responses to all serotypes; depending on the dose, maternal-to-infant antibody ratios were approximately 0.4 to 1.3.

"The potential protective concentrations that are reported herein are based on a single seroepidemiologic study," the authors write. "Future studies are needed to better define these immunologic relationships."

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