The book is not an anti vaccination treatise but an attempt to introduce the concept that vaccination can inculcate a diseased state onto the vital force which Burnett called vaccinosis. The aim of the book is to show that a) there exists a diseased state of the constitution which is engendered by the vaccinal virus vaccinosis or vaccinial state b) there exists in nature a notable remedy for said vacinosis Thuja occidentalis by reason of its homoeopathicity c) applicability of law of similar to the prevention of disease. The book teams up with acute and chronic cases of vaccinosis showing the ill effects and consequences of vaccination and contribution of Thuja as a preventive medicine according to the law of likes & dynamics homoeoprophylaxis. An attempt has been made to study the nature of Homoeoprophylaxis and the importance of law of similiars in prophylaxis through examples.