Well, that's a very thorny issue, of course, but all responsible Christian Scientists obey the various laws concerning reportable illnesses, broken limbs and the like. I've never been vaccinated before (though I'm frequently anaesthetised for dentistry of course), but if I were to go abroad to somewhere exotic, it would be my legal and moral obligation to comply with travel regulations.
I'm not trying to be an apologist, but at least the concept behind CS healing is no more silly than various alternative or holistic practices, which (believe me) we get an awful lot of them here in the Cotswolds!