| Summary |
1. The titer of lyophilized seed virus has not decreased significently for 33 month at 10 to 20°C; stored at 2 to 5°C , the vaccine was stable for 16 month.
2. Injected to 5-month-old N. D. antibody free chickens, its immunity period was about 6 month.
3. On booster injection, its immunity period was one year.
4. Past intramuscular injection 7 to 8 days the chicken has very strong infectious protection ability.
5. With contact control test we has not fond any contact infection case.
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