“…After its first report in Canada (3), this variant has spread globally, causing increases in the incidence of serogroup C disease in many countries, including the Czech Republic in 1993 (36), Greece in 1993 (33), and Norway in 1994 (63). This epidemic triggered a number of major public health interventions worldwide, including mass immunization (6,15,52) and the accelerated introduction of the serogroup C conjugate vaccine (44). As seen in all three carrier collections, ST-11 complex meningococci normally occur at a low prevalence among carriage isolates (12,20,23,47); however, during 1993, a year before the collection of most of the Czech isolates used in the present analysis, there were unusually high levels of ST-11 serogroup C carriage in the Czech Republic, possibly due to the recent spread of the variant (30).…”