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What Is The Difference Between The Pfizer and Moderna COVID-19 Vaccines

January 20, 2021

Two COVID-19 vaccines are now authorized for use in Canada by the Food and Drug Administration. Pfizer and Moderna are helping in the fight against COVID-19 with two new vaccines.

Understanding the Vaccines 

Both the Pfizer/BioNTech and the Moderna vaccine are mRNA vaccines.

According to the CDC, traditional vaccines, like the flu shot, put a weakened or inactivated germ into our bodies. The mRNA vaccines are different in that they teach our cells how to make a protein - or even a piece of protein - that triggers an immune response, producing antibodies that protect us.

Viruses contain a core of genes made of DNA or RNA wrapped in a coat of proteins. To make the coat of protein, the DNA or RNA genes of the virus make messenger RNA (mRNA); the mRNA then makes the proteins. An mRNA of a specific structure makes a protein of a specific structure. 

In the case of COVID-19, it triggers a spike protein, The spike protein is found on the surface of the virus that causes COVID-19.

COVID-19 mRNA vaccines are given in the upper arm muscle. Once the instructions (mRNA) are inside the immune cells, the cells use them to make the protein piece. After the protein piece is made, the cell breaks down the vaccine and gets rid of the virus.

How effective are they? 

The effectiveness of both the Pfizer and Moderna vaccines are about the same. Both vaccines are administered in two doses and have similar effective rates. After the second dose, Pfizer’s vaccine is 95% effective, Moderna’s 94.5%. 

Vaccines typically prevent illness, not infection, which means people could theoretically still carry the virus even if they were inoculated against it. Since SARS-CoV-2 can be spread by those without symptoms, having a vaccine that also prevents transmission is important.

How many doses will I need? 

Two doses are required for both vaccines. However, the time between the initial shot and the booster differs. The Pfizer vaccine calls for a booster 21 days after the first dose. Moderna's vaccine comes after 28 days.

How are they stored? 

Both vaccines need to be kept cold. However, Pfizer's vaccine needs to be extremely cold. The Pfizer vaccine is stored at temperatures between -112 to -76 degrees Fahrenheit, is distributed in a five dose vial, and must be diluted with .9% sodium chloride before being administered.

The Moderna vaccine is stored at temperatures between -13 to -5 degrees Fahrenheit, is distributed in a ten dose vial and does not have to be diluted before administration.

Both can be stored for up to six months. The warmer temperature of Moderna's makes storing and shipping the product more manageable, which could help in getting the vaccine to more remote areas of the country.

Which vaccine is best for me? 

Pfizer’s vaccine has been approved for use in people over the age of 16, the Moderna vaccine has been approved for use in people over the age of 18. According to the FDA Canada, Moderna’s vaccine will also be administered 28 days apart, compared to Pfizer's 21 days.

Moderna performed clinical trials on 30,350 participants, while Pfizer performed 36,621 clinical trials, both had successful results between an approximate 94-95% improvement rate.


What are the most common side effects of both vaccines?


The most commonly reported side effect for both vaccines was injection site reaction and injection site pain 

Pfizer/BioNTech Covid-19 Vaccine -84.1%

Moderna Covid-19 Vaccine -91.6%

Additional commonly reported side effects:


Pfizer/BioNTech Covid-19 vaccine:

  • Injection site reaction -84.1%
  • Fatigue -62.9%
  • Headache -55.1%
  • Muscle pain -38.3%
  • Chills -31.9%
  • Joint pain -23.6%
  • Fever -14.2

Moderna Covid-19 Vaccine:

  • Injection site pain -91.6%
  • Fatigue -68.5%
  • Headache -63%
  • Muscle pain -59.6%
  • Joint pain -44.8%
  • Chills -43.4%


In the case of both the Pfizer/BioNTech and the Moderna Covid-19 Vaccine, we still do not know how long immunity lasts, and whether booster shots will be required down the road. 

We also do not know how long a vaccination rollout will take to reach the masses across all of Canada. The government has said it hopes to vaccinate the majority of Canadians by fall 2021. Regardless of where you stand on the topic of the COVID-19 vaccines, be sure to keep practicing safe and healthy measures like wearing proper masks, PPE, and social distancing when required to keep you and your loved ones safe during the pandemic.

*This article is not meant to be taken as medical advice. Please follow the advice of your local health authorities when making decisions about your own health and the people around you.
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