title: Questions vaccine efficacy trial.
mesh_terms: D000818:Animals; D002417:Cattle; D002418:Cattle Diseases / Q000517:prevention & control*; D010326:Pasteurella Infections / Q000517:prevention & control* / Q000662:veterinary*; D012766:Pasteurellosis, Pneumonic / Q000517:prevention & control*; D014611:Vaccination