Immunization in Canada: current controversies.

Immunization, once used solely to control a disease, is now sufficiently widespread that elimination or even eradication of certain diseases has become possible. However, with greater control of disease, adverse reaction to immunization has taken on new prominence. Reporting of adverse reactions varies widely across Canada, and may be due to administrative differences-some provinces rely mostly on the public sector for immunizations, others on the private sector. Several controversies over immunizing agents remain, for example, live versus killed poliovirus vaccine, but generally immunization in Canada is now relatively uniform and safe.