Cluster of serogroup W invasive meningococcal disease in a university campus.

Introduction: In France, the expansion of an hypervirulent strain causing serogroup W invasive meningococcal disease (MenW) has been observed since 2015/16. We describe a cluster of three MenW cases, causing two deaths, at the end of 2016 in a university campus, and the vaccination campaign which was consequently organized.

Methods: Epidemiological and microbiological analyses led a multidisciplinary expertise group to recommend the organization of a mass vaccination campaign using ACWY vaccine targeting more than 30,000 students and staff in the university campus. Individual data on vaccination was collected using the lists of students and staff registered at the university to estimate vaccine coverage.

Results: Three MenW cases occurred within a 2-month period among students in different academic courses. All three isolates were identical and belonged to the "UK-2013 strain" phylogenetic branch. The attack rate was 10.8/100,000 students. The vaccination campaign was organized only 15 days after the third case occurred. In total, 13,198 persons were vaccinated. Vaccine coverage was estimated at 41% for students of the university and 35% for university staff.

Conclusion: Timely notification of cases to health authorities was essential for the detection of the cluster and the rapid implementation of the vaccination campaign. No further cases occurred in the campus in the year following the vaccination campaign. This episode is the second cluster of MenW caused by the "UK-2013 strain" in a university since 2016.