1 The titer of 1yophi]iI si virus has not decreased signuficently for 33 month at -10 to-20'C; stored at 2 to 5'C, thevaozinewas sb1efor16month.
2.Jnfrted to 5-month-old N. 0, antilxdy flee chickens, its immunity reriod was about 6 month.
3.On booster in jection, it's immunity pericd was one year.
4.Past int-amuscu]ax infrtion 7 to 8 days the chicken has very sfrong in&tious gotDton ability.
5.With contact control ntol test we has not fond any cc’ntsct infection case.