>>108 >>125
引用文のすぐ近くに書いてある内容ぐらい読めよ。

>>108
However, the leaky vaccine changes this evolutionary pressure and permits
the evolution of highly virulent strains. The vaccine's inability
to prevent infection and transmission allows the spread of highly
virulent strains among vaccinated chickens. The fitness of the more
virulent strains is increased by the vaccine.

"leaky"ワクチンだから、接種済み個体間で強毒株が生き残ってしまうって事。
モンタニエ博士が言ってたのと同じ事。

>>125
The disease would cause mild paralysis, with the only identifiable
lesionsbeing in neural tissue. Mortality of chickens infected with
Marek's disease was quite low.

当初低かった死亡率が変異の結果100% に達したって事。