Immunogenicity of a serogroup B meningococcal vaccine against multiple Neisseria meningitidis strains in infants

Background.. The serogroup B meningococcus is responsible for the majority of cases of meningococcal disease in temperate countries. Infants and young children < 2 years of age are at greatest risk of disease. This study asse ssed the immunogenicity in infants of a serogroup B meningococcal outer mem brane protein vaccine that has been used extensively in disease outbreaks i n Cuba and several Latin American countries and shown to be efficacious in teenagers. Method. One hundred five healthy infants entering the routine vaccination s chedule in Havana, Cuba, were given either 2 or 3 doses of the serogroup B meningococcal vaccine VA-MEN-GOC-BC at 3.5, 5.5 and 7.5 months of age. Immu ne response pre- and postvaccination was determined by the conventional ser um bactericidal assay (SBA), a more sensitive novel whole blood bactericida l assay (WBA) and immunoglobulin ELISA. Results. In 52 and 46% of infants > 50% killing of the vaccine serogroup B strain (BA:P1.19,15) and serogroup C strain, respectively, was demonstrated by the WBA after 2 doses of the vaccine. Serum bactericidal activity (4-fo ld increase in titer) was induced in only 27% against the vaccine serogroup B strain and in 14% against the serogroup C strain. The changes in WBA and SBA were mirrored by the serogroup B and C immunoglobulin ELISA. Cross-rea ctive immunogenicity against other (heterologous) serogroup B strains was d emonstrated for one of the four further strains assessed by WBA. By age 16 to 18 months SBA, WBA and ELISA responses had declined considerably. The ad dition of a third dose of vaccine did not appear to significantly influence immunogenicity at 17 months of age. Conclusion. The serogroup B outer membrane protein vaccine VA-MENGOC-BC ind uces a demonstrable immune response in infants against both the serogroup, B vaccine strain and against a serogroup C strain. Cross-reactive immunogen icity against other (heterologous) serogroup B strains is limited in this a ge group.