Step1OK=Passive decline <line> of maternal antibodies. <line> All chicks do not have <line> the same maternal antibody level <line> at day old. <line> Some have a level above <line> average, others below average, <line> the uncertainty on the flock <line> average is represented by <line> the colored area.&&Step2500=Limit of vaccine take for an <line> Intermediate Plus vaccine: 500.&
&Step2250=Limit of vaccine take <line> for an Intermediate vaccine: 250.&&Step3500=Vaccination must ideally <line> be performed when the maternal <line> antibody level reaches <line> a value of 500.&
&Step3250=Vaccination must ideally <line> be performed when the maternal <line> antibody level reaches <line> a value of 250.& &Step3Prec=Choosing too early <line> a vaccination date will result <line> in the vaccine virus <line> being neutralized <line> by maternal antibodies.&&Step3Tard=Choosing too late <line> a vaccination date.&&Step4OK=It allows the vaccine to induce <line> active immunity and raise <line> the antibody level again. <line> Therefore, birds will be properly <line> protected against the wild virus.&&Step4Prec=The vaccine will not be able <line> to induce the production <line> of antibodies: birds will not be <line> protected against the wild virus. <line> The production of antibodies <line> will be low or null.&&Step4Tard=The maternal antibody level <line> will drop below the limit <line> of protection against <line> the wild virus. <line> As long as the maternal antibody <line> level is below the limit <line> of protection against a natural <line> infection, birds are receptive <line> to the wild virus.&&Step5OK=Therefore, birds will be properly <line> protected against the wild virus.&&Step5Prec=The production of antibodies will be low or null.&&Step5Tard=As long as the maternal antibody level is below the limit of protection against a natural infection, birds are receptive to the wild virus.&