An effective vaccine against dengue is very difficult to achieve. Because of ADE, infection with an unvaccinated strain following a single-strain vaccination could lead to the more severe symptoms associated with secondary infections (Halstead and Deen 2002) . Therefore, an effective vaccine must protect against all four serotypes simultaneously. A recent theoretical study on a 2 strains system (Billings et al. 2008) has shown that eradication of dengue using only single-strain vaccines is unlikely. Because a tetravalent vaccine is not immediately forthcoming, deepening our understanding of the dynamics of dengue in more realistic models is of great importance.