Abstract: The analysis of the potential impact of the meningococcal vaccines in asymptomatic
carriers has become one of the key aspects in the evaluation of new vaccines and of their
impact on disease control. An important step in this direction is provided by the analysis of the
sequence variability and surface-exposure of the 4CMenB (Bexsero®) vaccine antigens, as well
as the cross-reactivity of vaccine induced antibodies, in isolates from healthy carriers. The
Spanish Reference Laboratory, in collaboration with the University Hospital Marqués de Valdecilla
in Santander (Spain), carried out a meningococcal carrier survey between May 2010 and April
2012 (population aged 4 to 19 years). The present study was done on 60 meningococcal carrier
strains representative of the overall strain panel obtained and compared to invasive strains
isolated in Spain in the same time. We found quantifiable levels of fHbp and NHBA expression and
immunologic cross-reactivity in 10% and 75% of analyzed carrier strains, respectively, so the
potential impact of the 4CMenB vaccine on Spanish asymptomatic carrier strains is expected to
be mediated by the NHBA antigen.
