Headlines - Vaccination Week: Let’s not forget the meningococcal C vaccine!

In France, 99% of invasive meningococcal infections (IMI) are caused by strains of serogroups A, B, C, Y, and W135. Serogroup C accounts for 25% to 30% of invasive strains identified at the National Reference Center (CNR), following serogroup B, which is the most common with an average of 60%. The frequency of invasive serogroup C strains exhibits significant cyclical fluctuations, notably peaking in 1992 and again in 2002, when it accounted for 42% and 38%, respectively, of the invasive strains identified at the CNR.

While one might have expected a more pronounced continued decline in the incidence of invasive meningococcal disease (IMD) caused by serogroup C between 2003 and 2008 due to the disease’s natural cycle, the moderate decline in incidence observed could be explained by the emergence of a new clone. Indeed, since 2005 in France, the establishment of a specific phenotype/genotype, C2a:P1.7,1, has been observed, whose frequency among invasive C strains rose from 1% before 2005 to 24% in 2008. These strains belong to the ST-11 clonal complex and, in particular, to the ET-15 clone, which was responsible for the increase in C-type IIM in the early 1990s in several countries and has been shown to be associated with high mortality, the occurrence of clustered cases, and a shift in the affected age groups (adolescents aged 15–19).

Within our two regions, clusters of IIM C cases had led health authorities to organize vaccination campaigns targeting children and young adults living in or frequenting the designated areas: in April 2006, this occurred in Migennes in the Yonne department, involving a C:NT:P1.2,5 strain belonging to the ST-11 clonal complex, and in Roulans in the Doubs department in June 2008, involving a C2a:P1.7,1 strain.

In light of these findings, while vaccination against meningococcal C was previously recommended only for at-risk individuals and those in close contact with a case of IIM C, the High Council for Public Health (HCSP), during its meetings of the Technical Committee on Vaccinations on April 24 and June 26, 2009, recommended routine vaccination of infants aged 12 to 24 months with a single dose of meningococcal C conjugate vaccine.

During the period required to achieve sufficient vaccination coverage to ensure herd immunity, the HCSP recommends extending routine vaccination up to the age of 24 years, following the same single-dose vaccination schedule.