Just make it an Opt-in rather than Opt-out !!!!
It is so f**king simple, if its made Opt-in then only the people with any interest in letting their private medical information be open for every man and dog to peruse at their leisure would join said stupid scheme !
Just like at the bottom of some forms they have a tick box for you to be opted-in to advertising BS, obviously most people don't tick the box, because most people are not that stupid or are they ?