For these reasons, the Meningococcal Antigen Typing System (MATS) is used to measure bacterial antigen expression in order to predict whether bactericidal serum is capable of killing particular strains. This method is characterised by both phenotypic and genotypic analyses: the expression of the individual antigens that cross-react with the corresponding vaccine antigen is quantified using polyclonal antibodies against NHBA, NadA, and fHbp in an enzymelinked immunosorbent assay (ELISA), and DNA sequence homology to the variable region sequence of the vaccine strain PorA gene is assessed, in order to estimate coverage in a specific region. It has not yet been proved that there is a correlation between the MATS results and real vaccination coverage, but the predicted protection based on the expression of at least one matched antigen ranges from 73% to 87% . The MATS has been applied to isolates of 1,052 MenB strains causing IMD in Europe submitted to reference laboratories in France, Germany, Italy, Norway, and the UK between 2007 and 2008, and the analysis demonstrated estimated efficacy values ranging from 73% in the UK to 87% in Italy. Furthermore, a study conducted in Canada between 2006 and 2009 analysed 157 MenB isolates collected from children and adults with IMD and found that the potential coverage of 4CMenB vaccine was 75–90%. On the basis of the MATS ELISA findings, the authors predicted that 66%of the circulating strains were covered by at least one vaccine antigen although none were covered by all four.