All you need to know about the different types of vaccines and how they work

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]
Ingredient	mRNA	mRNA	Adenovirus vector	Adenovirus vector
Dose	Two	Two	Two	One
Eligibility	12+ years	18+ years	18+	18+ years
Efficacy	95% 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 dose	62% effective after two weeks of receiving the second shot	66% effective following two weeks after vaccination
Side effects	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)	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	-70^oC	-20^oC	2^oC to 8^oC	2^oC to 8^oC

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.

Disclaimer: The information provided in this response is for general informational purposes only and is not intended to be legal advice. The content provided does not create a legal client relationship, and nothing in this response should be considered as a substitute for professional legal advice. The information is based on general principles of law and may not reflect the most current legal developments or interpretations in your jurisdiction. Laws and regulations vary by jurisdiction, and the application and impact of laws can vary widely based on the specific facts and circumstances involved. You should consult with a qualified legal professional for advice regarding your specific situation.

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/