The third part, Vaccines, addresses Europe’s need for novel vaccination strategies for populations at risk. To this end the project includes the development of novel mono-valent vaccine candidates – vaccine candidates that can protect against either WNV or CHIKV – and bi-valent vaccine candidates – vaccines candidates that can protect against both WNV and CHIKV. A bi-valent vaccine is especially useful in areas where WNV and CHIKV circulate simultaneously. We develop and subsequently perform rational improvements of vaccine candidates, resulting in safer and more efficient vaccine combinations for the clinical development that are tailored specifically to the situation in Europe. This is combined with supporting studies on cross-protection of different WNV lineages, to guide in the development of (one) vaccine candidate(s) that can protect against the different circulating WNV strains. Furthermore, standardised neutralisation and other immune response assays are developed, which will allow accurate comparison of the protective capacity of different vaccines, which is a critical step forward in determining the most suitable vaccine candidates.