There is a crucial difference between vaccinosis and a vaccine reaction, which can have significant clinical implications. Unfortunately, in much of the discussion around vaccination, this distinction becomes blurred. A vaccine reaction, if properly managed, need have no adverse effects, but failure to recognise it and act accordingly can lead to the creation of a vaccinosis. Vaccinosis can also be established as a primary condition. The imperatives and protocols involved with vaccination vary considerably between the medical and veterinary professions, but our common homeopathic approach provides us with the means of assessing every situation from the perspective of the body's reaction, and thus to appreciate the true significance of what is happening to our patient.