This
finding had been reported by Mass et al. 1999 who
compared the dose-response effects of three
inactivated ND vaccines. The results showed that
chickens vaccinated with different doses of 1/12.5,
1/25, 1/50, 1/100, 1/200 and 1/400 had a similar
dose-response curve on serologic response and
clinical protection for the three vaccines.