Janssen COVID-19 vaccine: What you should know 

Many potential drugs and vaccines for use against COVID-19 are being evaluated in Canada and around the world. We’re closely tracking all potential drugs and vaccines in development.

You can search the complete list of applications received for COVID-19-related drugs and vaccines and their status.

On this page

About the Janssen COVID-19 vaccine

The Janssen COVID-19 vaccine (Ad26.COV2.S) is used to prevent COVID-19. This disease is caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).

The vaccine is approved for people who are 18 years of age and older. Its safety and effectiveness in people younger than 18 years of age have not yet been established.

Health Canada authorized this vaccine with conditions on March 5, 2021, under the interim order respecting the importation, sale and advertising of drugs for use in relation to COVID-19.

Find detailed technical information about the Janssen vaccine, such as the product monograph and our regulatory decision summary, in the COVID-19 vaccines and treatments regulatory portal.

Janssen regulatory information


How it works

Viral vector-based vaccines use a harmless virus, such as an adenovirus, as a delivery system. This “vector” virus is not the virus that causes COVID-19. Adenoviruses are among the viruses that can cause the common cold. There are many different types of adenoviruses, and many have been used as delivery systems for other vector-based vaccines for decades.

When a person is given the vaccine, the vector virus contained within the vaccine produces the SARS-CoV-2 spike protein, which is found on the surface of the virus that causes COVID-19. This protein will not make you sick. It does its job and goes away.

Through this process, the body is able to build a strong immune response against the spike protein without exposing you to the virus that causes COVID-19.

How it’s given

A single 0.5mL dose of the vaccine is given by injection into the muscle of the arm.

Based on studies in about 43,000 participants, the Janssen COVID-19 vaccine was 66% effective in preventing symptomatic COVID-19 disease beginning 2 weeks after vaccination. Immunity develops over time. You won’t develop significant protection against COVID-19 for at least 2 weeks.

Possible side effects

In general, the side effects observed during the clinical trials are similar to what you might have with other vaccines.

The side effects that followed vaccine administration in clinical trials were mild or moderate. They included things like pain at the site of injection, body chills, feeling tired and feeling feverish.

These are common side effects of vaccines and do not pose a risk to health.

As with all vaccines, there’s a chance that there will be a serious side effect, but these are rare. A serious side effect might be something like an allergic reaction. Speak with your health professional about any serious allergies or other health conditions you may have before you receive this vaccine.

Health Canada has conducted a rigorous scientific review of the available medical evidence to assess the safety of the Janssen COVID-19 vaccine. No major safety concerns have been identified in the data that we reviewed.

Vaccine safety after authorization

As for all medicines, Health Canada will continue to monitor the safety of the Janssen COVID-19 vaccine in Canada closely. Along with the Public Health Agency of Canada and working in close collaboration with the provinces and territories and the manufacturer, we will monitor for any adverse events that may develop after immunization.

Once the product is on the market, the manufacturer (Janssen Inc.) is legally required to submit reports of adverse events to Health Canada.

The manufacturer is planning to follow clinical trial participants for at least 1 year after the vaccine is given. It must communicate any safety concerns to Health Canada.

To ensure that the benefits of the vaccine continue to outweigh the risks, we may also impose terms and conditions at any time. For example, we can require the manufacturer to take further risk mitigation measures. We can also ask the manufacturer to submit additional safety information.

Health Canada will continue to review all the available safety data as it becomes available. We will take appropriate action, if required, to protect the health and safety of Canadians.

Related links

Did you find what you were looking for?

What was wrong?

You will not receive a reply. Telephone numbers and email addresses will be removed.
Maximum 300 characters

Thank you for your feedback

Date modified: