I would put > 50/50 odds on there being a human alive today with at least one CRISPR-edited germline variant. I think the question is now how can we regulate/control CRISPR germline editing; not how can we prevent it.
Human embryo gene editing was reported in May 2015 (http://dx.doi.org/10.1007/s13238-015-0153-5). It's reasonable to assume that the editing took place significantly before the submission date, especially given reports that the paper was first rejected from several other journals on ethical grounds (http://www.nature.com/news/chinese-scientists-genetically-mo...). I'm not trying to suggest that these particular scientists have performed experiments on viable embryos also, but I'd be very surprised if someone hasn't.
Human embryo gene editing was reported in May 2015 (http://dx.doi.org/10.1007/s13238-015-0153-5). It's reasonable to assume that the editing took place significantly before the submission date, especially given reports that the paper was first rejected from several other journals on ethical grounds (http://www.nature.com/news/chinese-scientists-genetically-mo...). I'm not trying to suggest that these particular scientists have performed experiments on viable embryos also, but I'd be very surprised if someone hasn't.