An improved method for freezing and storing frozen Marek's vaccines

Instead of using the traditional glass vials to hold the vaccines during storage in liquid nitrogen containers, a new plastic straw is utilized. Same batches of monovalent (HVT or Rispens CVI-988) or bivalent (HVT + Rispens) vaccines have been frozen in glass vials and in straws in programmable deep-freezer. The quality of the vaccine in straws is improved because during the freezing-cycle a greater surface of vaccine is presented, that results in better survival of cells (+8% trypanbleu dye exclusion test) and also better preservation of the virus in the cells (+18% PFU/dose). It means more cells and an higher titre in comparison with the glass vials. The straws are unbreakable and more compactable in the nitrogen-liquid containers, saving space in storage and delivery.