Wow that's a tough question. (I love that movie by the way!) I really don't know if I would go for it. On one hand you're saving so many other lives, that in many cases are also innocent lives meaning that they didn't bring the disease upon themselves, but taking a child's life would be so difficult. Taking any innocent life would be difficult. Could you really live with yourself after doing that?
I know this is in caritas, but I have to link it back to Buffy. In the episode "Dead Things" this theme is played out when Buffy tries to turn herself into the police.
BUFFY:A girl is dead because of me.
SPIKE: And how many people are alive because of you? How many have you saved? One dead girl doesn't tip the scale.
BUFFY:That's all it is to you, isn't it? Just another body!
SPIKE: Buffy-
BUFFY: You can't understand why this is killing me, can you?
Taking one innocent life would rip any moral person apart. I don't know about this one. I'll have to think about it for a while.