The AstraZeneca COVID-19 vaccine (ChAdOx1-S) was approved for use in Canada on February 26, 2021. Canada has authorized two manufacturers of this vaccine:
These vaccines are the first viral vector-based vaccines authorized in Canada to prevent COVID-19.
Medicinal ingredient: Adenovirus vector vaccine (ChAdOx1-S)
Do NOT take the AstraZeneca vaccine if you:
If you have any symptoms that could be due to COVID-19, talk with your healthcare professional about your symptoms and getting a COVID-19 test.
Health Canada has approved the vaccine 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.
The National Advisory Committee on Immunizations (NACI) has updated the recommendations on as a result of rare condition of blood clot formation following vaccination. While previous recommendation included offering the vaccine to adults 55 years of age and older, the latest recommendation, based on current evidence, is that the use of AstraZeneca vaccine may now be offered to adults 30 years of age and older. However, in Ontario, it is individuals 40 years of age and older who are eligible to receive this vaccine.
Pregnant individuals may choose to receive the vaccine at any time during their pregnancy. However, essential consideration should be made for those in the later stages of their pregnancy.
It is recommended, but not required, that pregnant individuals have discussion with their treating health care provider, or with a health care provider familiar with their pregnancy, that includes:
Please see the COVID-19 Vaccination Recommendations for Special Populations for further details on COVID-19 vaccination for pregnant individuals.
You will require 2 doses of the vaccine. It is recommended that the two doses be given between 4 and 12 weeks apart.
COVID-19 viral vector-based vaccines use a harmless virus (adenovirus) which is modified and used as a delivery system for making the SARS-CoV-2 spike protein. The vector virus used is not the virus that causes COVID-19 infection (SARS-CoV-2).
Adenovirus is a common virus that can cause cold-like symptoms, but it is safe to use as it has been modified and cannot cause infection.
Once immunized, the virus vector enters cells and provides instructions to make the SARS-CoV-2 spike protein. Like with natural infection, when the immune system is exposed to parts of the spike protein an immune response is initiated. This leads to the creation of antibodies. These antibodies allow the immune system to recognise, respond and protect the person if exposed to COVID-19 virus at a later time.
Immunity develops over time. It takes about 2 weeks to develop significant protection against COVID-19. For the greatest protection, you will need the second dose.
In clinical studies, the average efficacy of the AstraZeneca vaccine against symptomatic COVID-19 infection was 62% beginning two weeks after the second dose.
Like other COVID-19 vaccines, the length of immunity from the Astrazeneca vaccine remains unknown. Currently, there is no evidence to suggest the need for booster doses of COVID-19 vaccine, after the two doses are complete. Research is ongoing.
COVID-19 vaccines are given as an intramuscular (IM) injection into the deltoid muscle (upper arm).
The side effects are similar to other vaccines. They are generally mild to moderate and are resolved within a few days. They include things like pain at the injection site, body chills, feeling tired, and feeling feverish. These are common side effects of vaccines, and do not pose a risk to health. With all vaccines, there is a chance of a serious side effect such as an allergy reaction, although these are rare. Speak with your health care provider before vaccination if you have a health condition or a serious allergy.
Health Canada has completed a rigorous scientific review of the available medical evidence to assess the safety of the AstraZeneca COVID-19 Vaccine. The vaccine is safe and effective, and no major safety concerns have been identified. There will be continued monitoring for the safety and efficacy of COVID-19 vaccines after authorization. Find more information on the safety of the vaccine on the Government of Ontario website.
Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT), blood clot formation along with low levels of blood platelets following vaccination is a rare adverse event associated with the AstraZeneca vaccine. There is a very small risk that these rare blood clots will occur following immunization with the AstraZeneca COVID-19 vaccine, occurring in 1 in 250,000 to 1 in 500,000 people.
Treatment for the potential rare side effect of blood clot formation after receiving the AstraZeneca vaccine is available. Individuals should seek urgent medical attention if any of the following symptoms develop following vaccination:
Health Canada has a robust vaccine safety system which begins at the vaccine development stage and continues even after vaccines are approved. It is due to this strong system that Health Canada was able to recognize the potential risk of rare blood clots that have occurred following vaccination with the AstraZeneca COVID-19 vaccine and take measures to review all available scientific data to refine recommendations, notify the public and healthcare providers to ensure transparency of this possible risk, and ensure ongoing safety of the vaccine.
As with all decisions in life one must balance risk and benefit. When making an informed decision about getting the AstraZeneca COVID-19 vaccine, it is important to consider that the risks of COVID-19 infection strongly outweigh the risks of the vaccine, this is especially true now that community spread of COVID-19 variants is evident across the district. The COVID-19 variants of concern increase the risk of infection, hospitalization, and death.
Consider these facts when making an informed decision about receiving this vaccine:
If you forget to go back to your healthcare professional at the scheduled time for your next dose, ask your healthcare professional for advice. It is important that you return for your second injection, or the vaccine may not work as well.
Even after getting your second dose, continue to follow public health measures like wearing a mask, physical distancing and washing your hands often. The vaccine is an additional tool in our fight against COVID-19. It is unknown how long immunity from the vaccine will last. In addition, not everyone is able to get the vaccine for various reasons. We must continue to follow public health measures to slow the spread of COVID-19. Monitor for symptoms of COVID-19 and get tested if symptoms present. There is preliminary evidence that the AstraZeneca vaccine may reduce asymptomatic infection, but the evidence is insufficient at this time to recommend stopping public health measures after vaccination.
All COVID-19 vaccines are good, and all vaccines will help fight the COVID-19 pandemic.
The authorization of additional vaccines in Canada to fight the pandemic can only help and provide additional support to respond to the pandemic as quickly as possible.
There are 4 vaccines approved for use in Canada and each report a different efficacy rate. The efficacy of different vaccines cannot be directly compared. Each vaccine was studied in a different clinical trial which were conducted at different times, using different populations and conditions. The authorized COVID-19 vaccines have not been compared in clinical trials.
Having additional vaccines authorized for use in Canada will provide the opportunity to better meet the vaccine dose volume needs so that more people can be vaccinated and protected against COVID-19 sooner.
Viral vector-based vaccines have the advantage of being easily transported and stored as opposed to mRNA vaccines.