Science & Technology

The Guide to COVID-19 Vaccines

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It has been just over one full year since Canada had its first confirmed COVID-19 case, on January 25th, 2020. Since then, the virus has gone on to infect over 750,000 Canadians and approximately 100 million people worldwide. The pandemic has fundamentally changed everyone’s daily life, and its reverberations will likely be felt throughout society and in the way we live for years or decades to come.

Recently, though, advances have been made and the end of the pandemic may just be starting to come into sight. Two companies have developed COVID-19 vaccines which, after rigorous clinical testing, have been cleared to be put to use on the general public. That is not to say that the pandemic will be ending soon, however; vaccine rollout has been challenging and many countries have had to delay their plans from what they were originally projecting.

One of the factors which makes distribution more difficult is the fact that the vaccines created by Pfizer and Moderna differ from each other in several key ways. Though their basic mechanism of action is the same, their compositions are not identical. This causes some disparities not only in how they are administered, but also how they are stored, manipulated, and transported.

Understanding the mRNA Vaccine

Though they differ from each other in many ways, the Pfizer and Moderna vaccines stick to the same basic mode of action. Both are what are called mRNA vaccines, named after the molecule they mimic in the body.

Messenger RNA, or mRNA, is produced in cells by “reading” DNA and transcribing it into a new type of molecule which is used as the “instructions” to create proteins. It is referred to as a messenger because it takes the basic genetic material in our DNA and transmits its “message” to the parts of the cell which create all the proteins that the body needs to survive.

Viruses work by mimicking RNA and tricking the cell into using its own mechanism to create more copies of the virus. This is how it multiplies and eventually takes hold of the body. The two COVID-19 vaccines contain mRNA which encodes the protein that constitutes the coronavirus’s recognizable spikes. This allows the body to gain an affinity for recognizing and fighting SARS-CoV-2 without actually having to introduce the dangerous virus into the patient’s body.

Despite both being mRNA vaccines and targeting the spikes of the coronavirus, these vaccines are far from the same, as the composition of a vaccine goes far beyond just the active ingredient. These differences explain the variations between the vaccines which complicate the process of deploying both simultaneously.

The Pfizer Vaccine

Well, technically it’s the Pfizer-BioNTech vaccine, but the latter company (a German biotechnology company) often gets omitted in the name of brevity. This was the first of the two vaccines to get conditionally approved for widespread use, with the official word coming from Health Canada on December 9th, 2020.

The vaccine is administered in two doses, given 21 days apart from each other through traditional shots in the arm muscle. According to a trial consisting of over forty thousand participants, the vaccine is 95% effective in preventing COVID-19 in people over 16 years old. However, full immunity only begins about seven days after the second dose, meaning that people can go up to one month after receiving their first dose before being fully immunized to the extent that the vaccine allows.

Of course, the vaccine also had to be demonstrated as being safe to use before it could be released to the wider public. The study demonstrated that the vaccine is highly unlikely to cause any severe incidents, though participants in the study often reported feeling minor headaches or fatigue for up to two days after receiving the vaccine. Concerns have been raised by some experts about a higher risk for allergic reactions from the Pfizer vaccine compared to most other vaccines, likely due to a compound in it called polyethylene glycol (PEG). While no studies have been done to test the allergenicity of the Moderna vaccine, it should be noted that it also contains the PEG compound.

Immunizing a whole population takes more than just developing a vaccine, however. The product must also be manufactured en masse and shipped all over the globe, and this is where the Pfizer vaccine poses a big challenge. In order to avoid degradation of the vaccine, it must be stored between -80℃ and -60℃, far colder than most commercial freezers, which very rarely ever dip below -20℃. This is so cold, in fact, that Pfizer has turned to ice cream manufacturer Dippin’ Dots, whose signature ice cream beads also have to be transported at lower temperatures than most freezers allow, to assist in the distribution of vaccines. Additionally, the design of shipment containers is such that the minimum order is 1000 doses, making it difficult for rural communities to order it, as local clinics may not have the capacity to hold so many doses and perform so many vaccinations.

The Moderna Vaccine

The second and most recent vaccine to be approved by Health Canada for widespread use was produced by American manufacturer Moderna. It officially received authorization to be distributed on December 23rd, 2020, two weeks after the Pfizer vaccine. As a result, less of a spotlight was shone on it at first, but it is actually advantageous to the Pfizer vaccine in several ways.

That said, it does still have its drawbacks, first and foremost that its mode of administration means it is about two weeks longer than the Pfizer vaccine after the first dose that the patient is immunized. The Moderna vaccine is also given in two doses, but these are given one month instead of 21 days apart, and it takes 14 days instead of 7 after the second dose for the vaccine to be fully effective. Once that point is reached, though, it is about as effective as the Pfizer vaccine, with a rate of about 94%. Trials have also shown that its safety numbers and concerns are largely similar to those presented by the Pfizer vaccine.

However, one area where the Moderna vaccine does offer advantages is transportation and distribution. Contrary to the extremely low temperatures necessary to preserve the Pfizer vaccine, this one’s ideal temperature is a much more manageable, but still very cold -20℃. Additionally, unpunctured vials of the vaccine last for 30 days in a fridge (2-8℃) compared to five days for Pfizer’s version, and at room temperature (8-25℃) it lasts for 12 hours as opposed to only two. These extended timeframes allow the Moderna vaccine to be stored inside clinics for long periods of time, making it more suitable for smaller clinics that do not have adequate freezers to store the Pfizer vaccine or enough traffic to use it all up in the short period before it expires, especially given the large shipment size.

Looking Ahead

These are the only two vaccines that have been approved in Canada in the United States so far, though companies such as Johnson & Johnson, Novavax, and CanSino Biologics all have candidates currently in the final stage of development, and there are many vaccines that have been approved elsewhere in the world. Regardless of these other possibilities, the main focus for Canada at this point in time remains the production, acquisition, and distribution of the Pfizer and Moderna vaccines.

The current priority is vaccinating high-risk individuals such as residents in long-term care homes, as well as front-line healthcare workers who could be exposed to the virus (and expose the virus to others) while on the job. The Government of Canada has stated that it wants to have these “target populations” fully vaccinated by the end of March, and then begin rolling out the vaccine to the general population by April, with the goal being to immunize everyone who wishes to be vaccinated by the end of 2021.

Thus, it will likely be a long time before the pandemic can be declared truly over, and even then, there is the possibility of COVID-19 returning as a seasonal illness in years to come. However, these developments do provide some hope as we near the one-year mark of the pandemic, a light at the end of the tunnel, leading back out to what a somewhat normal life, one which, even once the last case of COVID-19 in the world is resolved, will surely never be exactly the same again.


Canada plans to vaccinate everyone who wants it by the end of 2021:

Covid-19: Moderna vaccine is nearly 95% effective, trial involving high risk and elderly people shows:

COVID-19 mRNA Vaccines:

COVID-19: Vaccine Storage and Handling Guidance – Pfizer-BioNTech and Moderna COVID-19 Vaccines:

COVID-19 Vaccine Tracker:

Covid map: coronavirus cases, deaths, vaccinations by country:

‘It wasn’t called COVID at the time’: One year since Canada’s first COVID-19 case:

Moderna COVID-19 Vaccine: What you should know:

Pfizer-BioNTech COVID-19 Vaccine: What you should know:

Pfizer’s vaccine raises allergy concerns:

Safety and Efficacy of the BNT162b2 mRNA Covid-19 Vaccine:

What the Dippin’ Dots ‘cold chain’ can teach us about COVID-19 vaccines:

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