You are here

Immunize BC > Safety

Vaccine development, approval and safety monitoring

Date last reviewed: 
Tuesday, Dec 03, 2024

On this page:

Information

Key points

 
  • The vaccines used in Canada are extremely safe. They are among the safest medical products available.
  • Before any vaccine is approved for use by Health Canada, it must go through in-depth testing to prove it is safe and that it works. 
  • It can take up to 10 years or longer for a vaccine to be developed and approved for use by Health Canada.
  • Even after a vaccine is approved for use, its safety is continuously monitored.
Because vaccines are given to healthy people, including children, they must meet very high safety standards—often stricter than those for many medicines used to treat illnesses.
 

Vaccine development

Developing a new vaccine is a careful and lengthy process that usually takes many years. It happens in three main stages:
 
1. Exploratory stage
 
In this first stage, scientists learn about the disease and try to understand how to create a vaccine that can protect the body from it.
 
2. Preclinical stage
 
Next, researchers test the vaccine in the lab using cells and animals (like mice) to check if it’s safe and if it causes an immune response. If the vaccine looks promising, it moves on to testing in humans.
 

What’s an immune response?

An immune response is how our body detects and fights harmful germs, like viruses or bacteria.
 
3. Clinical stage
 
This stage consists of three phases of testing in humans (called clinical trials):
 
Phase 1: A small group of under 100 people receives the vaccine. Researchers check its safety and how well it causes an immune response.
 
Phase 2: Hundreds of people receive the vaccine, including those who are similar to the target group (in age, health, etc.). Researchers determine the best dose and schedule while continuing to check its safety.
 
Phase 3: Thousands of people take part in this phase. Researchers test the vaccine’s safety and effectiveness in large, diverse groups of people.
 
 

Vaccine review and approval

After clinical trials are complete, vaccine manufacturers submit their data to Health Canada. A team of experts at Health Canada carefully evaluates the data on the vaccine’s safety, effectiveness, and quality, and makes sure the manufacturing process meets strict standards.
 
Health Canada will only approve a vaccine for use in Canada if there is strong evidence that:
 
  • The vaccine is safe
  • It works 
  • It meets manufacturing standards
  • The benefits outweigh any potential risks
If a vaccine does not meet these criteria, it will not be approved. 
Fact

Did you know?

Vaccines usually take years to develop, but with global cooperation and funding, they can be created much faster. This was the case with COVID-19 vaccines, which were developed quickly thanks to advances in science and technology, increased funding, and international collaboration among scientists, health experts, governments, and industry.

Recommendations for use

In Canada, the National Advisory Committee on Immunization (NACI) reviews all available scientific evidence on the safety and effectiveness of approved vaccines. Based on this information, NACI makes recommendations on how vaccines should be used. The committee is made up of experts in fields like pediatrics, infectious diseases, and public health and follows strict conflict-of-interest rules.
 
Each province and territory in Canada is responsible for developing its own publicly funded vaccination programs. They use NACI’s recommendations, along with other information, such as local data on how often certain diseases occur, to create vaccination schedules for children and adults.
Fact

Did you know?

Health Canada reviews all aspects of vaccine production by manufacturers to ensure safety, efficacy, and quality. Even after a vaccine has been approved for use in Canada, every batch of vaccine is laboratory-tested for safety and quality.

Ongoing safety monitoring

After a vaccine is approved, its safety continues to be closely monitored.
 

Why is ongoing monitoring necessary?

Although vaccines are thoroughly tested for safety before approval, some side effects are so rare that they may not appear in clinical trials, even with thousands of participants. Once a vaccine is given to millions of people, these rare side effects—or those that occur more often than expected—can be identified.
 
Continuous safety monitoring helps keep the vaccine safe for everyone and allows health officials to respond quickly if any issues come up.
 

How is vaccine safety monitored?

Vaccine safety is monitored through two main methods: passive surveillance and active surveillance. Both methods track adverse events following immunization (AEFIs).
Information

What is an adverse event following immunization (AEFI)?

An AEFI is an unwanted or unexpected health event that happens after someone gets a vaccine. These events may or may not be caused by the vaccine. If you or your child experiences an AEFI, report it to your immunization provider, clinic, or health care provider. Reporting helps keep vaccines safe for everyone.

Passive Surveillance
 
In passive surveillance, health care providers and individuals (or caregivers) report adverse events following immunization. Here's how it works:
 
  • If someone experiences an adverse event, they should report it to their health care provider.
  • The provider then reports the event to public health authorities.
  • A local medical officer or nurse reviews the event and makes recommendations for future immunizations.
  • The BC Centre for Disease Control (BCCDC) collects and reviews all reports from around the province to spot any safety concerns. 
  • The Canadian Adverse Events Following Immunization Surveillance System (CAEFISS) tracks, and analyzes reports from across Canada to identify safety issues.
  • The World Health Organization (WHO) monitors vaccine safety worldwide, collecting data from over 75 countries, including Canada. 
Vaccine manufacturers must also report any serious side effects to Health Canada, whether they happen in Canada or elsewhere.
 
Collecting and analyzing reports at all these levels helps detect rare or unexpected side effects, ensuring that vaccines continue to be safe for the public.
 
Active surveillance
 
Active surveillance involves actively looking for and gathering data on adverse events.
 
In Canada, the SPRINT-KIDS network is responsible for this type of monitoring. It includes 15 children's hospitals, including BC Children’s Hospital.
 
  • Teams at these hospitals review the records of children who visit the emergency department or are admitted to the hospital to see if their condition may be linked to a recent vaccination.
  • SPRINT-KIDS also monitors how well vaccines protect children from respiratory diseases and tracks the spread of serious illnesses that vaccines can prevent.
  • If an AEFI is identified, they will report it to local health authorities and CAEFISS.

Identifying safety signals and determining the cause of adverse events

When a possible safety issue with a vaccine is found—called a "vaccine safety signal"—health experts carefully investigate it. A safety signal suggests there might be a link between a vaccine and an unexpected health problem or a change in how often or how serious a known side effect is. However, a safety signal doesn’t automatically mean the vaccine caused the problem.
 
If there’s concern about a side effect, experts investigate whether the vaccine might actually be the cause. This usually involves epidemiological studies—which look at patterns of health problems in large groups of people—along with reviewing data from different sources, consulting expert committees, and sometimes doing laboratory studies or pathological tests to find direct evidence of a link. Experts also look for similar signals in other safety networks to help determine if the problem is happening more often than expected.
 
In most cases, the events are not caused by the vaccine and are just a coincidence (something that happened by chance). But experts carefully check all the data to make sure. If a safety concern is confirmed, health officials can act quickly to protect the public, such as by removing a vaccine from use or stopping its distribution if needed.
 
Determining whether an adverse event is caused by the vaccine or by something else, like an infection or other condition, can be difficult. That’s why every reported event is thoroughly reviewed, and in some cases, further tests are conducted to better understand the cause. This careful process ensures that any real issues are identified and addressed.