A new vaccine (the 4CMenB 4-component protein vaccine [Bexsero], which includes 
PorA, factor H-binding protein [fHbp], neisserial heparin-binding antigen 
[NHBA], and Neisseria adhesin A [NadA]) against serogroup B meningococci has 
recently been approved for use in people older than age 2 months in Europe, 
Australia, and Canada. Preapproval clinical efficacy studies are not feasible 
for invasive meningococcal disease because its incidence is low/very low, and 
the serum bactericidal antibody (SBA) titer (or the human SBA [hSBA] titer when 
human complement is used in the assay) has been used as a surrogate marker of 
protection. However, the hSBA assay cannot be used on a large scale, and 
therefore, a meningococcal antigen typing system (MATS) was developed. MATS 
combines conventional PorA genotyping with an enzyme-linked immunosorbent assay 
(ELISA) that quantifies both the expression and the cross-reactivity of 
antigenic variants. The assay has been used to evaluate the potential of the 
4CMenB meningococcal group B vaccine to cover group B strains in several 
countries. Some recent data suggest that MATS is a conservative predictor of 
strain coverage. We used pooled sera from adolescents and infants to test by the 
hSBA assay 10 meningococcal group B strains isolated in Spain that were negative 
for the 3 antigens (n = 9) or that had very low levels of the 3 antigens (n = 1) 
by MATS. We found that all strains were killed by sera from adolescents and that 
5 of the 10 strains were also killed, although at a low titer, by sera from 
infants. Our data confirm that MATS underestimates vaccine coverage.