Mixed results for dengue vaccine trial

The results of the first trial of the effectiveness of a vaccine for dengue, a sometimes fatal disease endemic throughout most tropical countries, have engendered both enthusiasm and disappointment. The vaccine proved safe, and it protected against three of the four dengue virus variants, or serotypes—but surprisingly, it provided no protection against the fourth. Scientists are stumped as to why and pondering what this means for the global fight against a serious public health threat. “For us, it’s encouraging. The vaccine technology clearly has a biological effect that prevents dengue,” says Derek Wallace, regional director of clinical development for Sanofi Pasteur, the French pharmaceutical firm developing the vaccine, who reported results online today at The Lancet. Other scientists are less positive. “True, the vaccine shows protection against three of the strains, but unfortunately—and this is very disappointing—overall it was not effective, showing no protection for the most common dengue strain circulating in...