793B became undetectable in Northern Italy after homologous vaccine application was discontinued

IBV of the 793B (4/91/CR88) genotype has been detected for more than 2 decades in European farm surveys and since 1989 in Italy. Live 793B vaccines were developed and these gave effective control of the disease. Nonetheless in all farm studies in the last 2 decades, 793B detections have continued to be a major proportion of all detections. This extended prevalence led interested parties to speculate that these may be merely detections of 793B vaccine. In an area of northern Italy where IBV diagnostics are performed on a monthly basis, 793B vaccination was stopped in early summer 2013. Since August 2013 no further 793B detections have been made.