Ozone, a molecule made up of 3 oxygen atoms (O₃),
is very unstable and really wants to exist in a two atom form (O₂) or as something else.
Oxidation (the attachment of the extra O atom to another atom or element) alters other molecules – and in the case of viruses and bacteria, it alters their RNA structure and instantly kills them.
Once oxidation is complete, all the ozone will have converted to oxygen – as harmless as nature intended.