By: Dilina Lallani

In response to the coronavirus (COVID-19) pandemic, manufacturers have created vaccines that target different cell pathways and create an immune response in the body to protect individuals from the virus. Although clinical trials are ongoing, there are four approved vaccines in Canada: Pfizer-BioNTech (Pfizer), Moderna, AstraZeneca-Oxford, and Janssen (Johnson & Johnson, also known as the J&J vaccine).

Comparison between approved vaccines in Canada 

 Pfizer-BioNTech [1]Moderna [2]AstraZeneca [3]Janssen (Johnson & Johnson) [4]
IngredientmRNAmRNAAdenovirus vectorAdenovirus vector
DoseTwoTwoTwoOne
Eligibility12+ years18+ years18+18+ years
Efficacy95% effective in those 16 years and above after one week of receiving the second vaccine dose

100% effective in those 12 to 15 years old after one week of receiving the second vaccine dose.
94.1% effective after two weeks of receiving the second dose62% effective after two weeks of receiving the second shot66% effective following two weeks after vaccination
Side effectsPain at the injection site
Body chills
Fatigue
Fever
Headache
Allergic reaction (ie. anaphylaxis)
Pain at the injection site
Body chills
Fatigue
Fever
Headache
Allergic reaction (ie. anaphylaxis)
Pain at the injection site
Body chills
Fatigue
Fever
Headache
Allergic reaction (ie. anaphylaxis)
Blood clots and low platelet counts
Pain at the injection site
Body chills
Fatigue
Fever
Headache
Allergic reaction (ie. anaphylaxis)  
Storage-70oC-20oC2oC to 8oC2oC to 8oC

mRNA versus adenovirus vector vaccines 

Messenger RNA (mRNA) is genetic material that plays a vital role in protein synthesis. mRNA vaccine uses genetic material to produce proteins that can later be recognized on a virus and trigger the production of antibodies to fight the virus. The COVID mRNA vaccine used in Pfizer and Moderna is a non-live virus that triggers an immune response in the body upon COVID-19 exposure. Once injected, the mRNA synthesizes the SARS-Cov-2 spike protein, which is a harmless component found on the surface of the COVID-19 virus [5]. Hence, if infected with COVID-19 in the future, the body will recognize the SARS-CoV-2 protein on the virus and trigger the immune system to respond by producing antibodies that attack and destroy the protein and the rest of the virus.

Viral vectors are often used as vaccine ingredients to inject harmless vectors, which are modified and harmless versions of viruses, to create an immune response in the body upon future exposure to a harmful virus. Adenovirus, a virus that causes a common cold, vectors are commonly used in vaccines. An adenovirus vector is used in the COVID-19 AstraZeneca and Janssen vaccines and produces the SARS-CoV-2spike protein, allowing the body to develop an immune response [6]. Viral vector vaccines have also been used in the Ebola vaccine. 

Variants and vaccine effectiveness

New variants from Europe, South Africa, India, and Brazil question vaccine efficacy. Most vaccines have been shown to be effective against the new variants. For example, studies demonstrated that Pfizer is effective in neutralizing the Alpha, Beta, and Delta variants [7]. 

If you have any questions about the COVID-19 vaccines, please contact your healthcare professional or visit https://www.canada.ca/en/public-health/services/diseases/coronavirus-disease-covid-19.html for the latest data and vaccine information.

References

[1] Government of Canada. (2021). Pfizer-BioNTech COVID-19 vaccine: What you should know. Website: https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/drugs-vaccines-treatments/vaccines/pfizer-biontech.html

[2] Government of Canada. (2021). Moderna COVID-19 vaccine: What you should know. Website: https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/drugs-vaccines-treatments/vaccines/moderna.html

[3] Government of Canada. (2021). AstraZeneca COVID-19 vaccine: What you should know. Website: https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/drugs-vaccines-treatments/vaccines/astrazeneca.html

[4] Government of Canada. (2021). Janssen COVID-19 vaccine: What you should know. Website: https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/drugs-vaccines-treatments/vaccines/janssen.html

[5] Government of Canada. (2021). COVID-19 mRNA vaccines. Website: https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/drugs-vaccines-treatments/vaccines/type-mrna.html

[6] Government of Canada. (2021). COVID-19 viral vector-based vaccines. Website: https://www.canada.ca/en/health-canada/services/drugs-health-products/covid19-industry/drugs-vaccines-treatments/vaccines/type-viral-vector.html

[7] National Collaborating Centre for Infectious Diseases. (2021). Updates on COVID-19 Variants of Concern. Website: https://nccid.ca/covid-19-variants/