Original antigenic sin is of particular importance in the application of vaccines. In dengue fever, the effect of original antigenic sin has important implications for vaccine development. Once a response against a dengue virus serotype has been established, it is unlikely that vaccination against a second will be effective, implying that balanced responses against all four virus serotypes have to be established with the first vaccine dose. However, in 2015, a new class of highly potent, neutralizing antibodies that is effective against all four virus serotypes has been isolated, bringing hope for the development of a universal dengue vaccine.