Received: 23 November 2021
Accepted: 7 June 2022
First Online: 29 August 2022
: The Medical Research Ethics Committee of Maastricht University Medical Centre (MUMC +) confirmed exemption of this study from official approval under prevailing laws in the Netherlands (number METC 2021–2880). All data presented in this paper, including information obtained from affected schools, were retrospectively retrieved from regular infectious disease control activities, were de-identified, coded and were analyzed anonymously in accordance with Dutch guidelines and regulations. No additional administrative permissions were required to use the data as it is owned by the South Limburg Public Health Service.
: Not applicable.
: The authors declare no competing interests.