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Viruses and Variants: What’s Up With The Booster?

By Maryann Makosiej

These days, boosters are all the rage. Meant to re-prime your immune system, you might have been like me and felt sicker than ever for about a day after. What’s the catch? Aren’t vaccines supposed to help me?

You might be wondering: “what exactly is in that little vial that causes those flu-like symptoms?” or even “where do viruses even originate from?” If so, you’ve come to the right place. With the development of the Omicron variant of SARS-Cov-2 and as we head indoors for the winter, boosters and other vaccines are more important now than ever. Let’s learn what they are all about.

What is a virus?

A virus is a microscopic parasite. It is an organism that lives within another organism and relies on it for reproduction (CDC Parasites, 2018). Viruses contain genetic information, like RNA or DNA, but they cannot reproduce themselves by themselves. They lack certain genetic machinery (like ribosomes) and a metabolism (Wessner, 2010). While this is where we come in as humans, animals and other organisms can also be infected by viruses.

Why do we feel sick when we’ve gotten a vaccine?

Remember that vaccines are teachers. They are meant to teach your immune system how to recognize and attack invading viruses if you ever encounter them. Boosters are a reminder. Like a study guide at the end of the semester, they remind the immune system of what viruses look like. When we get chills, fever, muscle aches, etc. after getting a vaccine (booster or not), what we feel is inflammation (Hervé et al., 2019). After the virus is introduced into the body, the immune system is quickly activated. Cytokines, lymphocytes, macrophages, and a litany of other cells and molecules go into action to recognize the invader and attack it (CDC Understanding How Vaccines Work, 2018). The symptoms are signs that the immune system is working.

Where do viruses even come from?

There are three ideas.

One, the Progressive (or escapist) Hypothesis, is dubbed progressive because of the time it took to occur. It states that viruses may have come from genetic elements that “escaped” from a host cell (Wessner 2010). These genetic elements eventually learned how to enter and exit cells and can explain why viruses still have enough genetic information to reproduce themselves.

The second idea is the Regressive (or devolution) Hypothesis. It states that some organisms may have found an evolutionary advantage to reproduce like a parasite (Wessner 2010). Parasites need others to survive; essentially, they cannot reproduce without a host and their host’s genetic information. It’s a simple way of life and it requires a lot less cellular machinery. The organisms shed their genetic information, devolving as it were, until they literally could not reproduce by themselves anymore. In this way, they regressed to become viruses.

Three makes a crowd and there is a third idea about where viruses come from. It’s called the Virus-First hypothesis and it states that viruses existed before their cellular hosts (Wessner 2010). They evolved independently. The evidence lies in that the very first replicating molecules consist of RNA. Some RNA molecules, like ribozymes, can catalyze/jumpstart chemical reactions. It may be possible, this theory argues, that simple RNA viruses today could be descended from these ancient and precellular RNA molecules.

So, who wins? Like the meaning of life or who took the last piece of cake, the answer is never straight-forward. Viruses are diverse. Some have RNA genomes and others have DNA genomes. Some have massive libraries of genetic information (Wessner 2010) and others just have a few books. What scientists do know is this: no clear explanation of where viruses come from has ever been articulated. Viruses probably do not come from one single common ancestor. They are varied and commonly exist in the environment. They are as much a part of us as we are of them. Getting your annual flu vaccine and COVID-19 booster, if you are able, helps to be proactive in our interaction. Wherever viruses come from, we know that they will continue to evolve. Our approach should too.


CDC - Parasites - About Parasites. (2018). Retrieved 28 November 2021, from

Understanding How Vaccines Work | CDC. (2018). Retrieved 28 November 2021, from

Hervé, C., Laupèze, B., Del Giudice, G. et al. The how’s and what’s of vaccine reactogenicity. npj Vaccines 4, 39 (2019).

Wessner, D. R. (2010) The Origins of Viruses. Nature Education 3(9):37

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