The very vaccines used to prevent a respiratory disease in chickens caused several recent outbreaks of the same disease at farms across Australia, according to a report published today (July 12) in Science. Different weakened versions of a live herpes virus used in the vaccines exchanged portions of their genomes, resulting in virulent, disease-causing strains. This suggests that such in-the-field genetic recombination is more common than previously thought, and has implications for both animal and human health.
“I think that we completely underestimate the role of recombination in [vaccine] viruses,” said veterinary virologist Etienne Thiry of the University of Liège in Belgium, who was not involved in the work. “All RNA and DNA viruses do recombine to different extents,” he said. In fact, recombination, also known as reassortment, was part of the method used by one of the two groups that recently succeeded in making the H5N1 bird flu virus ...
