Author summary
dengue, Dengue, yellow fever, yellow fever vaccine, dengue infection
DENGUE, DISEASE, RARE DISEASES, YELLOW FEVER, DENGUE
Dengue and yellow fever are diseases endemic to tropical regions, often occurring in the same areas. There are highly effective vaccines against yellow fever, but there remains an unmet need for a dengue vaccine which can be used in people regardless of previous dengue infection. As multiple vaccines are often given together, particularly in travel medicine, we investigated the immunogenicity and safety of co-administration and sequential administration of a yellow fever vaccine and a tetravalent dengue vaccine (TAK-003) in adults living in areas of the US non-endemic for either disease. Most participants did not have pre-existing antibodies to either disease. We found that there was no reduction in immune response to the yellow fever vaccine when given at the same time as the dengue vaccine. There was also no reduction in response to dengue serotypes 2, 3, and 4, but this could not be established for the response to serotype 1. When sequentially administered, temporary increases were observed in yellow fever seroprotection rates after receipt of TAK-003, and in dengue seropositivity rates after receipt of the yellow fever vaccine, but these differences among groups were no longer seen by the end of the study. Both vaccines were well tolerated with acceptable safety profiles.