Zika virus co-circulates with dengue in tropical and sub-tropical regions. Cases of co-infection by dengue
and Zika have been reported, the implication of this co-infection for an integrated intervention program
for controlling both dengue and Zika must be addressed urgently. Here, we formulate a mathematical
model to describe the transmission dynamics of co-infection of dengue and Zika with particular focus
on the effects of Zika outbreak by vaccination against dengue among human hosts. Our analysis
determines specific conditions under which vaccination against dengue can significantly increase the
Zika outbreak peak, and speed up the Zika outbreak peak timing. Our results call for further study
about the co-infection to direct an integrated control to balance the benefits for dengue control and the
damages of Zika outbreak.