Optimum time interval between the first vaccination and the booster of sheep for Clostridium perfringens type D

The goal of the present study was the determination of optimum time interval between the first and second vaccination of sheep against Clostridium perfringens type D with aluminium hydroxide-adjuvanted monovalent vaccine. Eight weeks after the first vaccination of 13 sheep aged 6 months, 12 animals had developed a higher and 1 animal a lower antibody titre than 0.1 IU/ml. which is protective under natural conditions. No correlation was found between the extent of the immune response and the length of the period between the immunizations in 24 sheep vaccinated twice at an interval of 2, 4 or 8 weeks. In spite of this, revaccination is suggested 8 weeks after the first immunization: because in this case most of the animals are protected continuously up to the time of the second vaccination, and the second antibody peak develops later. This vaccination schedule provides protective immune response for the longest period of time.