2yr old's medical info being sold

My 2yr old had to have a pescription filled for the first time the other month. He is now receiving mail addressed to him at our home address from companies asking him to participate in clinical research studies. I am worried about how his information was received and how much of his info was sold/handed out. I have called our peditrician, the pharmacy and the companies, no one has answers on how his info was handed out. How can i find out who handed out this information and violated his medical privacy? Is there a way to stop it? Is this a HIPPA violation?

 

Thanks. I'm not looking to get 'lawsuit crazy', just want to stop the letters. And he's only 2, just worried about how much of his info is out there and how far it all gets sold and used.