Rodolphus saw Lucius' reaction to the mention of Dragon pox but did not remark on it. He knew of the death of Lucius' father from the disease and in part that was what had made him pick that particular plan from the three the Healer had presented to him as definite possibilities. There was a certain... pleasure in taking a disease that could kill purebloods and turning it on those who were not.
"I had intended to vaccinate everyone here in Upper Slaughter but your thought of not telling them why is a valid and wise one," he said thoughtfully. "After all, even if there are no spies, you and I both know how... opportunistic some can be. Information about this plan of mine would be valuable to the right people, after all."
He chuckled. "I do like that idea," he said thought he did not elaborate. He'd had his eyes on a few of his Death Eaters who had been acting strangely. It might be worth trying this little trap on them.