NEW ORLEANS, LA—GSK Vaccines’ investigational meningococcal vaccine against serogroups A, B, C, W and Y (MenABCWY) is broadly effective among adolescents, according to the company’s Phase 2b, observer-blind, multicenter study, reported during a poster presentation at IDWeek 2016.

“This is the first study showing VE [vaccine effectiveness] of MenABCWY against a broad panel of endemic U.S. serogroup B invasive disease strains in healthy adolescents using a direct serological assessment,” reported Jo Anne Welsch, PhD, of GlaxoSmithKline BV, in Amsterdam, Netherlands. “The study results support previous estimates for breadth of coverage for endemic serogroup B strains using Meningococcal Antigen Typing System.”

The five serogroups account for almost all cases of invasive meningococcal disease. Their incidence varies geographically and year to year, Dr. Welsch noted. Previous research suggested that MenABCWY induces “robust immune response against vaccine-specific antigens” with acceptable safety, Dr. Welsch reported. 

The new study examined its effectiveness against a panel of U.S. endemic N. meningitidis serogroup B invasive disease strains, among healthy children aged 10–18 years.

A total of 305 adolescents were enrolled and randomly assigned (1:1) to receive either two doses of MenABCWY or placebo at baseline and MenACWY-CRM vaccine at Month 2; 301 participants received vaccinations.

The study employed a panel of 110 serogroup B strains, representing 25% of the entire CDC repository of U.S. invasive meningococcal disease isolates. Endogenous complement human serum bactericidal assay (enc-hSBA) were measured at baseline and 1 month after second vaccination (M3) to assess antibody levels against the panel strains.

“At baseline, the mean percentage of seronegative subjects (without bactericidal activity at 1:4 dilution) across all strains was 80% in both groups,” Dr. Welsch noted. “At M3, the mean percentage of seronegative subjects declined to 25% in the MenABCWY group and remained similar (76%) in the MenACWY-CRM group.”

Vaccine effectiveness at M3 was 67% (95% CI: 65–69).

“At baseline, most subjects in both groups had bactericidal antibodies against <20% of tested strains, with 5%–7% of subjects having antibodies against >50% of strains,” Dr. Welsch reported. “At M3, 97% of subjects in the MenABCWY group were protected against >50% of tested strains and 59% were protected against >70% of strains; protection in the MenACWY-CRM group was unchanged from baseline.”

The study was funded by GlaxoSmithKline Biologicals SA. Dr. Welsch and other coauthors are employees of the company.