Meningococcus C vaccine was first used in France to prevent epidemics. It was a success in Puy-de-Dôme, Landes, Pyrénées Atlantiques and Hautes Pyrénées. Following many European countries, France introduced meningococcus C conjugate vaccine in 2009 but this recommendation was not suffiicently applied (6,6% of the 20-25 years-old were vaccinated in 2015).

The situation in France is very different from UK and there is no data on the subject. The vaccination campaign in 2002 in Puy-de-Dôme offers much more detachment, possible comparison between vaccinated and unvaccinated people, among which meningococcus circulation could maintain immunity. This is the reason why we have decided to assess in 2016 the vaccinal and natural immunity among Puy-de-Dôme population.

People were recruited during hospitalisation or consultation of Pediatric, Occupational Medecine, Infectiology departments of Clermont Ferrand Hospital or Health Service of Auvergne's University, from March to September 2016.

Doctors gave informations about the study and collected consents before blood tests were done (two tubes of 4,5mL each).

Blood tests were daily collected and freezed. Then they were analysed at Meningococcus National Reference Center, in Paris.

Inclusion Criteria:

• - people from 13 to 39 years old
• who received meningococcus C conjugate vaccine in 2002 in Puy-de-Dôme (vaccinated group) or not (unvaccinated group)

Exclusion Criteria:

• vaccination before or after 2002 containing meningococcus C valence
• refusal to participate