Worldwide, the meningococcal bacterium is responsible for a severe, and sometimes lethal infection: invasive meningococcal disease (IMD). Infection can quickly progress into severe illness or death, despite quick and adequate medical care including antibiotic treatment. Vaccination is crucial in the prevention of IMD by inducing the production of antibodies that prevent development of this disease. In the Netherlands, meningococcal serogroep C (MenC) vaccination was included in the national immunization program (NIP) for children 14 months of age in 2002. Because of an outbreak of IMD caused by serogroup W, MenC vaccination was replaced by a MenACWY vaccination at age 14 months in 2018. In addition, MenACWY vaccination was implemented at the age of 14 years and a catch-up campaign for 14-18 year-olds was performed in 2018-19. This campaign in 2018-2019 was very effective; a reduction of 82% in the number of IMD-W disease cases was found among vaccinated minors and 100% reduction in teenagers. We evaluated protective antibody levels at all ages in consecutive population-based serosurveys in the Dutch population. We found that meningococcal seroprevalence was low, except in vaccinated groups, implicating the need for meningococcal immunization strategies in case of future outbreaks. We estimated that the duration of protection after a MenACWY vaccination ranges from several years in adults to more than 30 years in adolescents. Finally, we showed that in case of immune modulating medication as in case of rheumatic disease or inflammatory bowel disease, targeted extra immunizations may be required. In conclusion, this thesis contributed to knowledge on meningococcal immunity after MenACWY vaccination and the protection on population level in the Netherlands.