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Anatomy of the leading Covid-19 mRNA vaccines

Updated: Jan 31, 2021

COVID vaccine made by Pfizer-BioNTech was the first to be approved for emergency use first in the UK, then Canada, and lastly in USA. Another vaccine produced by Moderna is in the pipeline set to be approved very soon. In fact the government of Canada has arranged for 168,000 doses of the vaccine to be shipped to Canada so it can be available for immediate use by the end of December. One thing that is common to vaccines made by both companies is that they are based on a new technology that uses mRNA. As we see slow but continuous roll-out of COVID-19 vaccine over the next several months or so, it is important to examine and understand this novel technology, as this is the first time mRNA vaccines will be made available for use outside of the clinical trials.


covid-19 demo: doctor preparing a vaccine for inoculation
Covid-19 vaccine illustration

What is a Virus?

To bring in some context, first let's talk about the fundamental make-up of a virus. A virus is basically made up of either a DNA or an RNA covered by a coat of protein. Technically a virus is not a living organism, as it is unable to replicate by itself. So what happens is the virus invades a cell, crosses over to the nucleus of the cell and takes over the genetic make-up of the cell by integrating into the cell's DNA, and replicating itself to produce more copies of itself. Furthermore, it begins to send out codes of information to instruct the cell how to behave, what proteins to make, what cells to attack and so on.


corona virus as viewed under an electron microscope
coronavirus microscopy

Traditional vaccine technology:

Before now in the pre-COVID era, vaccines are most commonly made up of either live weakened virus, dead inactivated virus or viral protein. The whole idea is introduce an agent that mimics the real virus into the body system, therefore priming the body's immune response to produce antibodies. These antibodies can then be used in case the person later encounters the same virus, or with the help of memory T-cells, the immune cells will quickly remember how to produce more antibodies to fight the virus. The old technology used viral proteins or particles that have been altered just enough to prime the immune system without producing a clinical infection. The only problem is this traditional method of producing vaccines is slow and time consuming.


Novel mRNA vaccine technology

This new technology uses an mRNA, a fabricated genetic code that instructs our body cells to produce a specific protein found on the envelope that coats the coronavirus. This particular protein has been shown to play a key role in the antigenic properties of the virus. That is, the virus attaches to and invades the human cells via this protein. Therefore the presence of the spike protein in the body is enough to mount an immune response that is similar the virus. The main advantage of this technology is that there is no risk of infection. The genetic code only carries the instruction to make the spike protein and not the virus itself. And once the genetic make-up of the infectious virus is known, the production of mRNA vaccine is much easier and quite efficient.


DNA vaccine, RNA vaccine
DNA double-helix structure

Safety of mRNA vaccines

Because the mRNA vaccine is new to clinical practice, the long term effect of vaccine is yet to be determined. There will be a robust post marketing surveillance to ensure people that receive the vaccine are being monitored at least for the next 2 years to detect any adverse reactions that were not detectable in the clinical trial. Although mRNA-based prophylactic therapy is new, the science behind it dates back to decades ago. It has actually been used in the treatment of some cancers. Based on what is known now, mRNA does not affect or invade the human DNA because it cannot cross the nuclear membrane. It cannot reach the nucleus. mRNAs are generally highly unstable, part of the reasons why they need to be stored in cool temperatures. Thus, the injected mRNAs are quickly cleared from the human cells as soon as the code has been decoded.

Within the limits of the clinical trials, the short term effects were found to be mild and tolerable, similar to existing vaccines such as flu shot. Common immediate side-effects observed include injection site pain, fatigue, headache, muscle pain, joint pain and chills. These side effects were said to be more pronounced after the second shot. Although there has been a few reports of severe anaphylactic reactions, the overall safety profile of the vaccines has made them crossed the approval line.


Differences between the leading vaccines (Moderna vs Pfizer)


differences in storage, dosing, efficacy for Pfizer vs Moderna Vaccine
Pfizer vs Moderna covid-19 comparison

Both vaccines have similar profile however the storage conditions of the Moderna vaccine may make it more attractive since it can be transported more safely to remote areas. There are many more vaccines still in the pipeline and so we may begin to see more players come into this market over the next few years. Kudos to the leading vaccine producers, but eventually it’s going to a game of patience to know the vaccine that can truly stand the test of time. While we all wait for the full roll-out of the vaccines, be sure to learn about other ways to boost your immune system. Stay and keep keeping safe.

vaccine preparation before inoculation
Vaccine preparation for injection

Disclaimer: all health information provided on this platform represent my opinion only and are for educational purposes only. Reading my blog is not intended to be a substitute for a visit to your local pharmacist, physician, dietitian, and other healthcare providers. Be sure to seek proper care from your nutritionist, family doctors or specialists when needed.


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