Put in the same situation, I don't think I could ever say that. I probably would be inclined to not say anything one way or another. How someone could lose a child but still become a champion of the cause I never got. And we see this happening a lot these days.
That quote is the only reason the story was published.
“She described her son as lovable and outgoing, and encourages people to get vaccinated.”
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The mother is saying this because her conscience would not be able to process the fact that in her case, having her child vaccinated potentially contributed to his death.