Clonal replacement and expansion among invasive meningococcal isolates of serogroup W in France

Our data suggest a recent clonal replacement among NmW/cc11 isolates with the expansion of the “South American-UK” sub-lineage in France and particularly the “UK 2013-strain” which was predominant in 2015 and 2016. A shift in the age-distribution of IMD due to NmW to older ages and the high CFR are consistent with the expansion of a new virulent clone in a naive population. These data may have an impact on tailoring vaccination strategies against NmW.