The research reported showed that: the stability of cell-free HVT vaccine, lyophilized and sealed under vacuum, is very high: after one year at 4 degrees -6 degrees C and after 10 days at 37 degrees C the titre decreased only about 0.4 log(10)', the stability of the vaccine, when reconstituted for use in the diluent (sucrose-phosphate buffer), is high (80%) for at least 2 hours; the degree of protection, found in 3 tests, was about 90% with an inoculum of 20 to 100 pfu, and the PD50 was 4.9 pfu of virus per chick.

SUMMARYThe research reported showed that: the stability of cell-free HVT vaccine, Iyophilized and sealed under vacuum, is very high: after one year at 4°-6°C and after 10 days at 37°C the titre decreased only about 0.4 log 10 ; the stability of the vaccine, when reconstituted for use in the diluent (sucrose-phosphate buffer), is high (80%) for at least 2 hours; the degree of protection, found in 3 tests, was about 90% with an inoculum of 20 to 100 pfu, and the PD 50 was 4.9 pfu of virus per chick.