Deworming and vaccination scheduled on the same day cut foot-and-mouth disease protection to 6.25 percent in sheep. Giving the FMD vaccine alone reached 37.50 percent. A second vaccine in the same session was worse still, dropping protection to zero by day 28. The antigen load is not the problem. Immune competition is. Why deworming and vaccination timing became a real problem Foot-and-mouth disease virus is a highly contagious pathogen of cloven-hoofed livestock, and vaccination is the most economical control measure available. The practical constraint on intensive sheep farms is labor. Catching and handling animals stresses the flock and costs the farm money, so producers fold interventions into one session: the…