Surveillance of Neisseria meningitidis Carriage Four Years After menACWY Vaccine Implementation in the Netherlands Reveals Decline in Vaccine-type and Rise in Genogroup E Circulation

Carriage of Neisseria meningitidis is an accepted endpoint in monitoring meningococcal vaccine effects. We applied molecular methods to assess the impact of menACWY vaccine implementation on meningococcal carriage and genogroup-specific prevalence in young adults in Fall of 2022, four years after the introduction of the tetravalent vaccine in the Netherlands. The overall carriage rate of genogroupable meningococci was not significantly different compared to the pre-menACWY cohort investigated in 2018 (20.8% or 125 of 601 versus 17.4.% or 52 of 299 individuals, p =0.25). Of n=125 carriers of genogroupable meningococci n=122 (97.6%) were positive for either vaccine-types menC, menW, menY or non-vaccine types menB, menE, menX and menZ, Compared with a pre-vaccine-implementation baseline, there was 3.8-fold reduction ( p <0.001) in vaccine-type carriage rates and 9.0-fold increase ( p <0.0001) in non-vaccine type menE prevalence. These findings imply that menACWY vaccination reduced circulation of vaccine-type meningococci, but lead to serogroup replacement in carriage. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work was supported by internal funds from the National Institute for Public Health and the Environment (RIVM) ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study protocol was reviewed by the Centre for Clinical Expertise at the RIVM. Since procedures were considered non-invasive, and participants were anonymized, the study was considered to be outside the scope of the Medical Research Human Subjects Act (http://www.ccmo.nl) and a Medical Ethical Committee issued waiver for additional ethical review. Informed consent was collected from all participants prior to inclusion and the study was conducted in accordance with the World Health Medical Association 1966 Declaration of Helsinki and the EU rules of Good Clinical Practice. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors