In that case, no viral infection has ever been eradicated outside the human body.
A cure is when it successfully guards against infection and destroys any virion remaining in the system through phagocytosis... and a vaccination is as close to that as you can get as it relies completely on the strength of your immune system to be effective. For a lentivirus to be used as a vector to destroy or break down cancerous cells is pretty damn effective and with further testing can lead to an effective remedy. It may not be a complete cure, but it is a cure by definition.
Learn some immunology.
cure
2 a: recovery or relief from a disease b: something (as a drug or treatment) that cures a disease
A cure is not complete eradication of a disease... only a preventative treatment against the symptoms it causes. Some cures can still allow you to pass on a disease even if you're cured of the symptoms since the virus is still present in your body (to an extent).
There are non-pathogenic strains of e. coli that are safe to use.
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