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Immunogenicity of 2 serogroup B outer-membrane protein meningococcal vaccines: a randomized controlled trial in Chile
J W Tappero1, R Lagos, A M Ballesteros
1Centers for Disease Control and Prevention, Meningitis and Special Pathogens Branch, Atlanta, GA 30333, USA. jwt0@cdc.gov
Insights
Serogroup B meningococcal vaccines showed efficacy in children and adults against homologous strains but not a heterologous epidemic strain. Epidemic strain-specific vaccines targeting class 1 outer-membrane protein (OMP) show promise for controlling outbreaks.
Area of Science:
- Immunology
- Vaccinology
- Epidemiology
Background:
- Meningococcal disease, particularly serogroup B, poses a global health risk.
- Serogroup B meningococcal disease disproportionately affects children younger than 4 years.
- Existing vaccine efficacy in this high-risk group remains unproven.
Purpose of the Study:
- To assess serum bactericidal activity (SBA) against homologous and a heterologous Neisseria meningitidis strain.
- To determine if SBA can serve as a correlate for vaccine efficacy against serogroup B meningococcal disease.
- To evaluate immune responses in infants, children, and adults following vaccination.
Main Methods:
- A double-blind, randomized controlled trial was conducted in Santiago, Chile, during a serogroup B epidemic.
- Infants, children (2-4 years), and adults received three doses of Cuban or Norwegian outer-membrane protein (OMP) meningococcal vaccine or placebo.
- Serum bactericidal activity (SBA) was measured at baseline, before dose 3, and 4-6 weeks post-dose 3.
Main Results:
- Vaccine recipients (children and adults) showed increased immune response to the heterologous epidemic strain compared to placebo.
- Infants did not demonstrate a significant immune response to the heterologous strain.
- High response rates (67-90%) were observed against homologous vaccine strains across all age groups, with class 1 OMP identified as the key immunodominant antigen.
Conclusions:
- Current serogroup B OMP meningococcal vaccines may not provide protection during heterologous epidemic outbreaks.
- Vaccines specifically targeting epidemic strains, particularly those homologous for class 1 OMP, are potential candidates for controlling serogroup B meningococcal disease.
- Further research into strain-specific vaccine development is warranted for effective disease control.
Context:
Meningococcal disease occurs worldwide, and serogroup B disease accounts for a large proportion of cases. Although persons younger than 4 years are at greatest risk for serogroup B meningococcal disease, vaccine efficacy has not been demonstrated in this age group.
Objective:
To evaluate serum bactericidal activity (SBA) against homologous vaccine type strains and a heterologous Chilean epidemic strain of Neisseria meningitidis as a potential correlate for vaccine efficacy.
Design:
Double-blind, randomized controlled trial conducted between March 14 and July 20, 1994. All blood samples were taken by December 1994.
Setting:
Santiago, Chile, where a clonal serogroup B meningococcal disease epidemic began in 1993.
Participants:
Infants younger than 1 year (n = 187), children aged 2 to 4 years (n = 183), and adults aged 17 to 30 years (n = 173).
Intervention:
Participants received 3 doses of outer-membrane protein (OMP) meningococcal vaccine developed in either Cuba or Norway or a control vaccine, with each dose given 2 months apart. Blood samples were obtained at baseline, prior to dose 3, and at 4 to 6 weeks after dose 3.
Main Outcome Measure:
Immune response, defined as a 4-fold or greater rise in SBA titer 4 to 6 weeks after dose 3 compared with prevaccination titer.
Results:
Children and adult recipients of either meningococcal vaccine were more likely than controls to develop an immune response to the heterologous epidemic strain. After 3 doses of vaccine, 31% to 35% of children responded to the vaccine vs 5% to placebo; 37% to 60% of adults responded to vaccine vs 4% to placebo (P<.05 vs control for all). Infants, however, did not respond. In contrast, against homologous vaccine type strains, the response rate was 67% or higher among children and adults and 90% or higher among infants (P<.001 vs control for all). Subsequent SBA against 7 isogenic homologous target strains identified class 1 OMP as the immunodominant antigen.
Conclusions:
These data suggest that neither serogroup B OMP meningococcal vaccine would confer protection during a heterologous epidemic. However, epidemic strain-specific vaccines homologous for class 1 OMP are promising candidates for the control of epidemic serogroup B meningococcal disease.
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