Covid-19 RNA Vaccines, Explained
As we approach a time when effective Covid-19 vaccines become available, I wish to explain to you all one further twist on these potentially life-saving medicines. All the major vaccine contenders now are RNA vaccines. What is an RNA vaccine, and are they safe?
First of all, what is a virus, exactly? A couple of biologists back in the Seventies made the delightfully snarky comment, “A virus is bad news wrapped in protein.” And that’s about the truth of it. Although viruses can do some remarkably complex things, they are blindingly simple in structure. A virus consists of the genetic material that codes for what it will do when it enters its targeted host cell—this can be DNA or RNA, depending on the species. And then there’s a protective protein coat, which contains all the devious machinery that allows the virus to enter that host cell once it encounters it.
That’s it. RNA and a protein coat. In Covid-19’s case, around 30,000 base pairs of RNA wrapped up in an absolutely weaponized protein coat, dang it, so effective is it at invading human lung cells.
Now, recall that there are several broad categories of vaccine types against viruses. Attenuated Vaccines contain a weakened form of the virus in question. Inactivated Vaccines contained killed virus, meaning that its DNA or RNA has been inactivated in some manner. And then Subunit Vaccines contain only some piece or fragment of the viral external protein envelope. Something that our body can recognize and mount an immune response to, but that does not contain any viral DNA or RNA.
This is the part that I truly hope I can help you all feel comfortable with. A Subunit Vaccine does not contain the genetic blueprint for the virus! A piece of protein is all it is. Sometimes when we get a Subunit Vaccine we feel a little off for a couple of days, but that’s from our immune response, not from the vaccine itself.
But how does a piece of a virus protect us against the whole virus? Well, our immune system can “recognize,” by making antibodies that fit them like lock and key, various different parts of the surfaces of viruses and bacteria. One good marker molecule is all it takes to fight the invader effectively.
It’s only the Covid-19 RNA that can harm us, and yet, select just the right piece of its protein coat (I believe they chose the "spike glycoprotein"), and that’s enough for our immune system to mount an effective response to the whole virus.
To make a Subunit Vaccine, a virus of concern is injected into many, many hen’s eggs, often for multiple generations, egg after egg after egg after egg, and each time incubated for several days to make more copies of the virus. Finally the fluid containing the virus is harvested from the eggs, the viruses are killed, and the desired viral proteins are cleaved off and purified over several days. Somehow, scientists are able to isolate and separate a specific viral coat protein from this yellow yolky mess, to use in their vaccine. There are also newer, recombinant subunit techniques, in which yeast is induced to manufacture the protein of interest, by altering its genome. All of these processes take six months and more to accomplish.
Oy! Complicated stuff. But at least we finally have the answer to that age-old question that periodically vexes us.
Why did the chicken cross the road?
Apparently, to get away from the egg-obsessed biologist!
In contrast to these time-consuming and labor-intensive methods, RNA vaccines induce some muscle cells in our arm, at the site of the inoculation, to make the viral coat protein. What scientists do is to identify the exact section of Covid-19’s RNA that codes for the desired coat protein. Then they cut that section of RNA out and isolate it. It’s been a huge challenge to stabilize that small section of RNA for shipping, and also to protect it from being instantly destroyed by the human immune system once injected. But they’ve done all that now, so here’s what happens when we get one of these RNA Subunit Vaccines:
The scrap of viral RNA that codes for the desired Covid-19 coat protein is injected into, say, our left arm. The muscle cells there say, “Oh, ok, here’s some RNA, I have to make this protein now.” Their ribosomes, our cells' amazingly cool protein-producing factories, read this scrap of RNA and assemble the Covid-19 coat protein. This vaccine RNA strand does NOT become a permanent part of our genes in any way; it’s not DNA, and it degrades completely in a day or two. It’s gone.
Meantime, thousands upon thousands of copies of the Covid-19 coat protein have been manufactured by ribosomes and pumped into our bloodstream. Our immune cells mount their response to what they perceive as a big threat, antibodies are made by the tens of millions, and voila! We have immunity to Covid-19 at long last. Without ever having been exposed to the whole virus at all. How long the immunity will last is currently unknown. It may be necessary to have yearly Covid-19 vaccines in order to maintain immunity.
(Best in Show Ribosome image from https://www.thoughtco.com/ribosomes-meaning-373363 )
RNA Subunit Vaccines can be made fast and, once made, adjusted and adapted with great speed when a virus mutates. They’re safe, fast and flexible. The one real concern is, what if the viral protein closely resembles something else in our body, and we end up with an auto-immune illness? This is possible with any vaccine, yet it seems unlikely with Covid-19. Humanity has been assaulted with so many coronavirus species for so many thousands of years that it's highly unlikely that the protein chosen for these vaccines resembles any of our own protein structures.
I hope this all eases your mind about receiving such a vaccine in the near future when they become available.
Once again, I’ll end with a quote from my favorite poem, A. E. Houseman’s Terence.
“Therefore, since the world has still
Much good, but much less good than ill,
And while the sun and moon endure
Luck’s a chance, but trouble’s sure.
I’d face it as a wise man would,
And train for ill and not for good.”
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