Fig. 1

A timeline of the IMD outbreak situation between September 2017 and September 2019. *Foundation Pharmaceutical Key Figures. These figures are a proxy for the number of vaccines administered outside the National Immunization Program and catch-up campaign, for example by general practitioners at the request of their patients. These figures exclude the vaccines administered by the public health services (GGD), who were in charge of administering the vaccines in the National Immunization Program and the catch-up campaign. These figures have been published elsewhere [2, 3]. ** Due to limited menACWY vaccine availability, the government had to adapt its policy regarding the menACWY catch-up vaccination campaign over the course of 2017–2019. In September 2017 (1 in figure), the Dutch government announced plans to implement a catch-up menACWY vaccination campaign for junior-high-school children (usually aged 12–14 years old). In March 2018 (2), the government communicated that due to the limited vaccine availability only children born between May and December 2004 (aged ~ 14 years old) would be invited for catch-up vaccination in 2018 and that children born in 2005 would be invited for vaccination in 2019. In July 2018 (3), the target group for the catch-up vaccination in 2019 was extended to all children born between 2001 and 2005 (all aged 14–18 years old, excluding those who would receive the vaccination in 2018) as more vaccines had become available. In December 2018 (4), it was decided to offer the menACWY vaccine in subsequent years to all 14 year old teenagers via the National Immunization Program