Efficacy, safety, and immunogenicity of a meningococcal group B (15:P1.3) outer membrane protein vaccine in Iquique, Chile. Chilean National Committee for Meningococcal Disease. 1995, Boslego, Vaccine

A clinical trial of a vaccine against serogroup B in Chile (40,000 people). As a placebo, a vaccine for other serogroups of meningococcus was used. The effectiveness of the vaccine for 2.5 years was 51%, and among children under 5 years, the efficacy was negative -23%.