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Helping you understand COVID-19 Vaccines

Our Medical Advisory Services Team (MAST) is the foundation of our Safe at Work System, providing evidence-based guidance to develop and implement time-relevant COVID-19 strategies.

The following primer, compiled by MAST, was designed to educate and empower employees and their families by addressing their most common vaccine-related questions.

COVID-19 vaccine stopping domino effect.

Why do we need vaccines?

By getting vaccinated, you can protect yourself, your loved ones, and your community. Vaccination is a massive step forward in ending the pandemic. However, to achieve herd immunity (when a sufficient portion of the population is immune so the virus cannot spread further), vaccination must be combined with social distancing, hand hygiene and proper use of masks and face coverings.

COVID-19 vaccines have been proven to be up to 95% effective in preventing symptomatic COVID-19 disease infection and up to 88.9% effective in preventing severe outcomes due to COVID-19.

How do vaccines work?

Vaccines teach your immune system how to fight a specific virus. Many vaccines introduce an inactivated virus—or part of the virus structure—into our bodies to trigger the immune system to develop antibodies that can fight that virus. This also prepares the immune system to recognize and remember how to fight the virus if exposed again in the future.

How do the new COVID-19 vaccines work?

The new Pfizer-BioNTech and Moderna COVID-19 vaccines are a new form of vaccines that use messenger RNA (mRNA), which instructs our cells to produce a harmless piece of the “spike protein” found on the surface of the COVID-19 virus. Once inside the cells, the mRNA creates the protein and displays it on the cell surface. Our immune system recognizes the abnormal spike protein and responds by creating antibodies against COVID-19. These antibodies will defend against future virus exposure.


Fact vs. Fiction

Fiction: “COVID-19 vaccines can give you COVID-19.”
Fact: Since the vaccines do not use the live virus, you cannot get COVID-19 from either of the vaccines.

Fiction: “mRNA vaccines change a person’s DNA.”
Fact: mRNA vaccines do not change a person’s DNA. We do not have enzymes to convert RNA to DNA.

Fiction: “The vaccines were developed and approved too quickly.”
Fact: Vaccine development is typically slow due to delays in funding and coordinating each stage of research. The COVID-19 vaccines were developed much faster due to improved technologies, and unprecedented cooperation and investment around the world. It is important to understand that no steps were skipped in bringing these vaccines safely to distribution. Also, mRNA-based vaccines have been in development for over 10 years.

Fiction: “We still need long-term data before we know the vaccines are safe.”
Fact: Just like other vaccines, COVID-19 vaccines went through a multi-stage process, with large trials involving thousands of people to ensure they are safe; in some cases, they were five times larger than other vaccine trials. Any side effects that occur are generally mild and/or infrequent, so it is very unlikely for lasting effects to develop. Long-term efficacy data to help understand how long protection lasts is being currently being collected.

Fiction: “Vaccine ingredients contain mercury, formaldehyde, aluminum and fetal cells.”
Fact: Neither the Moderna nor Pfizer-BioNTech vaccines contain mercury, formaldehyde, aluminum or fetal cells.

Fiction: “Once vaccinated, we don’t need masks, physical distancing or other COVID-19 prevention practices.“
Fact: Since there currently isn’t enough evidence of the vaccines’ duration of protection and effectiveness in reducing transmission, it is still recommended to follow COVID-19 prevention practices following vaccination—including physical distancing and the use of personal protective equipment (PPE) like masks and face coverings.

Are the COVID-19 vaccines effective?

Pfizer-BioNTech has reported a 95% efficacy rate and Moderna a 94% efficacy rate for their vaccine’s ability to prevent mild and severe COVID-19 symptoms. MAST physicians stress that it is possible to still be infected once vaccinated but at a much lower risk, and that the vaccination can prevent the disease from becoming more severe. This efficacy is applicable across racial and ethnic groups and both sexes. However, regarding efficacy across age groups, the Pfizer vaccine is currently approved for those aged 16 and older, while the Moderna vaccine is approved for those aged 18 and older.

What do we know about the new U.K. and South African COVID-19 variants? Are the vaccines effective against them?

Early evidence suggests that the U.K. and South African variants are more easily transmitted. However, there is not yet sufficient evidence to determine whether the vaccines will be effective or ineffective against new COVID-19 variants. Vaccine producers have expressed confidence that the vaccines can be re-engineered to protect against these new variants within 6 weeks.

Are the COVID-19 vaccines mandatory?

It is not mandatory to get vaccinated against COVID-19. Ultimately, the decision is yours.

Making the decision to get vaccinated

Although COVID-19 vaccines are safe, they are accompanied by common side effects as well as rare cases of adverse events.

Immunocompromised, pregnant and breastfeeding women

The Moderna and Pfizer-BioNTech clinical trials did not include pregnant and breastfeeding women, nor did they include immunocompromised individuals. If you fall into either category, be sure to consult your physician prior to vaccination.

Should I get vaccinated if I have already contracted COVID-19?

There is currently no evidence of how long the antibodies from a COVID-19 infection will last, therefore the National Advisory Committee on Immunization (NACI) and Centres for Disease Control and Prevention (CDC) recommends getting the vaccine to protect yourself, your loved ones, and your community.

What are the side effects?

A sore arm, fatigue and mild headaches are common side effects of the COVID-19 vaccines. It seems that these symptoms can worsen after the second dose, however, arm soreness should improve within 48-72 hours. One in 10 people will experience muscle aches, chills or a mild fever. This is consistent with what is experienced after a normal flu vaccine. While the rate of severe allergic reactions to the mRNA vaccines have been higher than those with the normal flu vaccine, they remain exceedingly rare at around one in 100,000 (or 0.001%) for the Pfizer-BioNTech vaccine. It’s important to note that if you are allergic to polyethylene glycol (PEG) or any PEG derivatives like polysorbates, you should speak with your healthcare provider prior to vaccination.

For more details on the Pfizer-BioNTech and Moderna vaccines, including ingredient lists, click here.

For live updates on the frequency of side effects for both vaccines, click here.

Person holding sore arm

How does the vaccination process work?

To be optimally effective, both the Pfizer-BioNTech and Moderna vaccines require two doses. spaced, respectively, three and four weeks apart. NACI and CDC highly recommend taking both doses to ensure maximum efficacy. If the vaccine doses are interrupted, it is not required to restart the first dose. Be sure to remain at the testing site for at least 15 minutes after vaccination so your symptoms can be monitored by healthcare professionals.

When can I get the vaccine?

The province or state in which you reside is responsible for the prioritization and distribution of COVID-19 vaccines, so be sure to visit your local government’s website for the latest updates. If you live in Canada, you can use this Vaccine Queue Calculator to estimate when you will be eligible. If you live in the U.S., you can use this Vaccine Queue Calculator to estimate how many people require vaccination before you.

To learn more about Medcan’s Medical Advisory Services, send a note to

Eat Move Think Podcast banner - episode 51- your COVID-19 Vaccine questions answered with Dr. Peter Nord

Soon, all adults will have the opportunity to get the COVID-19 vaccine. In this timely and informative podcast episode, host and CEO Shaun Francis joins chief medical officer Dr. Peter Nord to answer the most pressing vaccine-related questions from clients and corporations—compiled by Medcan’s Medical Advisory Services Team (MAST). For complete show notes and a full episode transcript, visit


How the Pfizer-BioNTech Vaccine works image –

Center for Disease Control and Prevention (CDC) –

Center for Effective Practice (CEP)-

National Advisory Committee on Immunization (NACI) –

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