The Covid-19 vaccines differ depending on their manufacturing process and the active component responsible for eliciting the immune response in the recipient. There are four types of vaccines against COVID-19: DNA, RNA, viral vector and inactivated.
It’s been almost two years since the novel coronavirus emerged, and we have come a long way in terms of finding new strategies to fight this ongoing COVID-19 pandemic. However, with more and more vaccines becoming available around the world, there is slight confusion in understanding the differences between them.
Currently, the available vaccines are the DNA, RNA, viral vector and inactivated types. I won’t be getting into the efficiency of each vaccine or stating which one is best. That is for you and your doctor to decide.
However, I will explain how each of these vaccines are made and how they differ from each other.
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The DNA vaccine – ZyCoV-D
ZyCoV-D, the world’s first DNA COVID-19 vaccine, is made by the pharmaceutical company Zydus Cadila.
This vaccine contains the DNA plasmid vector that carries the gene for the coronavirus spike protein. This spike protein is crucial for the virus to infect us, as these proteins bind to certain receptors called angiotensin-converting enzyme 2 (ACE2) receptors.
These receptors are commonly present in our cells, and upon interaction with the spike protein, the virus basically fuses with our cells and enters it. This is why the spike protein is the commonly used vaccine target, as it’s a key player in infection.
The DNA is shot into a recipient’s arm using a gene gun (don’t worry, it’s not painful), where the immune cells present under the skin gobble it up.
All DNA is read in a particular manner. This is called the ‘Central Dogma’, which explains how genetic information flows through the body. DNA is transcribed to messenger RNA (mRNA), which is further translated to proteins.
Once gobbled up, the DNA is processed by our own cells and enters the nucleus. Then, by using our own cellular machinery, the DNA will be transcribed into mRNA. From there, the mRNA will be translated by our cells to produce the spike proteins.
Our immune cells will spot these spike proteins and go “that’s not ours!” and will begin fighting it. This trains our body to recognize and fight spike proteins so that in the event of an actual infection, our body knows what to look out for.
There are currently 2 RNA COVID vaccines – the Moderna vaccine (mRNA-1273) and the Pfizer-BioNTech (BNT162b2) vaccine. You may be a bit more familiar with these two names.
These two vaccines use mRNA technology. Messenger RNA is simply genetic information that codes for a protein.
So, in the case of mRNA vaccines, the mRNA that codes for the spike protein is directly injected into the recipient’s muscles. Once inside, the mRNA is processed by our cells and our own cells begin to produce the spike protein inside our body. Similar to the DNA vaccine, our immune cells start to recognize these spike proteins as foreign and launch an immune response against them.
How are DNA and RNA vaccines different?
You may be wondering by now… if RNA vaccines are better, as the transcription step is skipped, why have DNA vaccines at all?
The difference is that mRNA does not enter the cell’s nucleus, unlike the DNA vaccine. This means that mRNA vaccines cannot affect our own genetic makeup. Additionally, once the mRNA is processed and the spike proteins are made, our body destroys the mRNA strand, removing it completely from our body.
With DNA vaccines, the genetic information remains in our cells, providing what we hope will be longer-lasting immunity.
Non-replicating viral vector vaccines
You may know these vaccines as the Oxford/AstraZeneca vaccine (AZD1222) or Covishield, Sputnik and the Johnson & Johnson vaccine (Ad26.COV2.S).
These vaccines use the most advanced technology for COVID vaccines – Adenovirus vectors.
Adenoviruses are viruses that cause mild and common symptoms like cold, sore throat and fever. These viruses aren’t exactly life-threatening, but this particular adenovirus is modified to carry the spike protein gene in its DNA.
You could call it a biological trojan horse, where it secretly carries the gene coding for the coronavirus spike protein. Once this vaccine is injected into the recipient, the virus enters the body and sets off an infection. Then, just like any other virus, it replicates using our own cellular machinery.
In doing so, the viral genetic information is processed, including the spike protein gene. As a result, our cells start producing spike proteins that are recognized by our immune cells.
In this case, a mild virus carrying our gene of interest is used in the vaccine, rather than just using plain genetic information. This process is more similar to the viral infection cycle.
Covaxin, an inactivated vaccine example, uses a modified version of the actual coronavirus (SARS-CoV-2).
This vaccine uses a modified version of the coronavirus, one that can’t replicate and grow inside our body. Once injected into the recipient’s arm, the virus stays in our body, waiting to be detected by our immune cells.
Once spotted by our immune warriors, they immediately scan and attack the viral particles and destroy them. This way, the immune system learns to recognize the entire viral particle and all its proteins.
There is another Chinese vaccine similar to this called CoronaVac.
With so many vaccines available around the world, it must be hard to stay informed about each kind, and the new options as they emerge. With over 100 COVID vaccine candidates being developed, the world will have a generous number of options to choose from.
However, with the rise in coronavirus variants, each vaccine may lose some of its efficiency. This is why governing bodies and medical experts recommend getting booster shots to keep your immunity high.
As you can see, there are quite a few vaccine types, each with its own advantages and disadvantages. Currently, no vaccine is recommended over another. As long as each one does its job and builds long-lasting immunity against the coronavirus in the body, they will continue to be given.
Remember, this article was not meant to tell you which vaccine is best. If you have yet to get your jab(s), consult your doctor to find out which one is best suited to you!