Authors’ response: Measles outbreak in Gothenburg urban area, Sweden, 2017/18: lower viral load in breakthrough infections Sundell, Nicklas and Dotevall, Leif and Lindh, Magnus and Westin, Johan and Liljeqvist, Jan-Åke and Bergström, Tomas and Studahl, Marie and Andersson, Lars-Magnus, Eurosurveillance, 24, 1900478 (2019), https://doi.org/10.2807/1560-7917.ES.2019.24.30.1900478