Is it permissible to combine supplications when seeing an afflicted person, and does that protect one from affliction?

It is permissible to change the pronouns in supplications to suit the condition of the supplicant or the one for whom the supplication is made. So, it is permissible for you to say, "Praise be to Allah who has cured us," using the plural form. It has been reported from the Prophet, peace and blessings be upon him, that whoever recites the supplication: "Praise be to Allah who has cured me from what He has afflicted you with, and has preferred me over many of those whom He has created with a great preference," upon seeing an afflicted person, will be cured from that affliction. This supplication includes those who are with him. It is recommended for the supplicant to say it to himself, silently, without the afflicted person hearing it.