If they're saying stop now I'm pretty sure it's too late. People just want to move on with their lives and will take whatever they can get and a doctor is sitting there telling them it's ok that choice is fine then jabbing it in their arm. People mix tons of things that go in their body every day, including for medical use. If it was really that potentially dangerous maybe it should have been made abundantly clear before people were even given an option to mix. You can't worry about the future too much you could have a bad reaction or you could get cancer or you could be just fine...why worry until it happens. If you have a very probable reason sure fix and work to prevent but it's got to be made clear to ppl because they are stubborn, also fear is not a nice motivation. :)