This is repository for the data and code used for the paper "Did the COVID-19 pandemic change the willingness to pay for an early warning system for infectious diseases in Europe?" published in 2021 in the European Journal of Health Economics (DOI 10.1007/s10198-021-01353-6). The repository contains a README file explaining the purpose of the different folders and files in the repository. The first part of the data (2018) was used in another publication in the European Journal of Health Economics from 2020 ([https://doi.org/10.1007/s10198-020-01171-2][1]). **Abstract:** The COVID-19 pandemic highlights the need for effective infectious disease outbreak prevention. This could entail installing an integrated, international early warning system, aiming to contain and mitigate infectious diseases outbreaks. The amount of resources governments should spend on such preventive measures can be informed by the value citizens attach to such a system. This was already recognized in 2018, when a contingent valuation willingness to pay (WTP) experiment was fielded, eliciting the WTP for such a system in six European countries. We replicated that experiment in the spring of 2020 to test whether and how WTP had changed during an actual pandemic (COVID-19), taking into account differences in infection rates and stringency of measures by government between countries. Overall, we found significant increases in WTP between the two time points, with mean WTP for an early warning system increasing by about 50% (median 30%), from around €20 to €30 per month. However, there were marked differences between countries and subpopulations, and changes were only partially explained by COVID-19 burden. We discuss possible explanations for and implication of our findings. [1]: https://doi.org/10.1007/s10198-020-01171-2