Bioethics Blogs

Ensuring Safe immunization

Karina Top describes the ways that data about vaccines are collected and used in Canada to ensure that immunization programs are safe.


Immunization is considered one of the 10 great public health achievements of the 20th century. Immunization programs have saved millions of lives and reduced the rates of diseases such as measles, diphtheria, and polio by more than 99%.  However, as rates of vaccine-preventable infections have declined, our collective memory of these serious diseases has faded. As a result, the public’s focus has shifted to the safety of recommended vaccines.

Vaccines are considered very safe, with benefits outweighing risks. However, adverse events are occasionally observed, most frequently fever, and swelling, pain, or redness at the injection-site. In rare cases (approximately 1–2 per 10,000 vaccinated individuals), adverse events can be severe enough to come to medical attention, for example allergic reactions or seizures. The continued success of immunization programs depends upon maintaining public confidence in the safety of recommended vaccines through rigorous surveillance and research.

Vaccine safety is tested at all stages of vaccine development: first in animal studies, second in human clinical trials, and third, after the vaccine is publicly available as part of a public health program. The ongoing safety of recommended vaccines is monitored by the Canadian Adverse Event Following Immunization Surveillance System, a collaboration of the Public Health Agency of Canada and the federal, provincial, and territorial health jurisdictions. Public health authorities conduct passive surveillance for severe or unexpected adverse events following immunization based on reports from healthcare providers. As well, the Canadian Immunization Monitoring Program, ACTive, searches for select adverse events among children admitted to any of the 12 participating pediatric hospitals.

The views, opinions and positions expressed by these authors and blogs are theirs and do not necessarily represent that of the Bioethics Research Library and Kennedy Institute of Ethics or Georgetown University.