Hepatitis B vaccination: risk-benefit profile and the role of systematic reviews in the assessment of causality of adverse events following immunisation.

Since the early 1990s, several cases of demyelinating diseases were reported in France in association with the vaccination against hepatitis B. A large scientific, regulatory, and public debate took place to reassure the growing concern of the population. The objective of this paper is to examine the decision process undertaken both in France and in Italy; to outline the main findings of the studies conducted before and after the French decision to suspend the vaccination campaign among adolescents; and to describe the contribution of systematic review and causality criteria in the evaluation of the risk-benefit profile of vaccines. Even on the basis of the early findings, which appeared to be compatible with a low increase in the risk associated with the vaccination, it was apparent that the risk-benefit profile was unchanged for newborns, and was essentially unchanged for adolescents and for high-risk adults. The availability of subsequent negative association studies provided further reassurance. It is essential to rely on well-conducted systematic reviews to produce valid and reliable estimates of the risk-benefit profile.