When Vaccines Turn Vicious | The Scientist

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.