I don't understand this kind of reasoning. You don't think that the 100s of PhDs that worked on this would have accounted for the riskiness of adding a live chickenpox virus vs not adding it? People need to start trusting experts more and do less of "common sense" over-thinking imo.
I feel a lot of people think the "experts" are conniving in their offices rubbing their hands together thinking up ways to be diabolical.