A review article recently appeared in the Lancet by Seligman and Gould, in which the authors raise a safety concern for flavivirus vaccines based on possible recombination between wild-type viruses and live, attenuated vaccine viruses. Flaviviruses are small enveloped viruses with a single positive sense RNA genome containing a single long open reading frame encoding three structural and seven nonstructural genes. There is considerable controversy about whether recombination events occur between flaviviruses. Unfortunately, by emphasizing this remote and theoretical risk, rather than the potential public health benefits of new vaccines, the authors have provided an unbalanced view that may impede the progress of a number of promising live, attenuated vaccines under development. Over 2.5 billion people are at risk of dengue, and this disease has a total impact of the same order of magnitude as malaria, tuberculosis, bacterial meningitis and others. The World Health Organization (WHO) and the Gates Foundation have placed a high priority on the development and introduction of live, attenuated vaccines against Japanese encephalitis and dengue.