Informing quarantine policy for measles control in primary school and daycare settings: insights from a simulation study, Flanders, Belgium

Abstract

Background: With a notification rate of 44.9 per million population in 2024, Belgium was among the countries with the highest measles rate of the European Union/ European Economic Area countries. Although the coverage of the first dose of measles-mumps-rubella (MMR) vaccination in Flanders was 96% in 2020, two-dose coverage was below 95%. To minimise the risk of sustained measles transmission in vulnerable settings, such as primary schools with low vaccination coverage or daycares, it is important to quarantine susceptible contacts of a measles case. Aim: We aimed to identify policies that balance measles outbreak control with societal as well as educational impact of quarantining children. Methods: Using a simulation model, we evaluated the impact of different quarantine strategies for measles in primary school and daycare settings in Flanders, Belgium. Results: We found that shortening the quarantine period from 21 to 18 days only moderately (e.g. 16-37% in primary school) increased the risk of a subsequent infection wave, and the final proportion of later-generation cases remained at most 3.2% of the school or daycare. In settings with a low vaccination coverage (e.g. 20%), multiple independent introductions or a low diagnosis rate (e.g. only half of symptomatic children going to a doctor), the addition of post-exposure vaccination can further reduce transmission risk. Conclusion: We found that quarantine duration could be shorter than the presumed maximal incubation period of 21 days, without substantially increasing the risk of onward transmission. As such, acceptability and compliance with mandated quarantine periods might also increase.