How do they occur, and can the current vaccines combat them?
Throughout the COVID-19 pandemic, not only has the virus rapidly spread across the globe, it has appeared to supernaturally evolve in order to maximize its risk of contagion and prevent its extinction. Luckily, the virus is not a superhuman being: it is merely undergoing genetic mutations as it rapidly replicates itself. But what causes these mutations, and what are their effects on vaccines?
Analyzing influenza virus mutations is helpful to further understand these mutations. To be clear, although both the influenza virus and coronavirus are contagious respiratory illnesses, they are caused by completely different viruses; however, they mutate similarly. Influenza viruses mutate in two main ways: antigenic drift and antigenic shift. Antigenic drifts involve multiple genetic copying errors accumulating over time (which, in reality, often happens quickly as viral cells replicate at an extremely rapid rate). A genetic mutation in a viral cell provides the RNA coding for slightly different spike proteins and antigens—substances on the surface of the virions that cause your body to build antibodies against them—until eventually your existing antibodies are no longer effective against the new antigens. Vaccines target spike proteins, and thus, even if you’ve gotten a flu shot, you can still get a mutated strain of the flu. While most antigenic drifts are benign, antigenic shifts can cause more rapid genetic changes to the virus. With the influenza virus, antigenic shifts occur when two different strains of the virus attempt to inhibit the same host cell at the same time, causing both strains’ RNA strands to mix in a process called reassortment. COVID-19 virions contain only one long strand of RNA, but they undergo a similar process: when two virions try to inhibit the same host cell simultaneously, their RNA strands recombine to make a new one. In both cases, the resulting “novel” virus often contains a new, different combination of spike proteins and antigens.
Thus, as it has spread and replicated across the globe, coronavirus has had the opportunity to undergo a multitude of mutations. The most drastic of these mutations is the Omicron variant. According to the Center for Disease Control (C.D.C.), “the Omicron variant is characterized by at least 30 amino acid substitutions, three small deletions, and one small insertion.” Omicron virions have an increased ability to bind to angiotensin converting enzyme-2 (ACE-2) receptor proteins, which is where coronavirus virions can dock, and are more capable of staying put, making the variant highly transmissible.
Can vaccines effectively respond to novel COVID variants? Different vaccines protect us from the coronavirus in different ways. The Pfizer and Moderna vaccines are mRNA vaccines, meaning they contain viral material that teach cells to make a harmless copy of a COVID spike protein. After creating the protein, T-lymphocytes and B-lymphocytes (our defensive white blood cells) destroy it, and will be prepared to do so again in the future if infected with the actual virus. The Johnson & Johnson vaccine is a viral vector vaccine, meaning that it injects a modified version of a different virus containing material from the coronavirus within it. Then, once again cells will make copies of the protein and the body will be prepared to fight actual infection in the future. Inevitably any COVID-19 vaccine’s effectiveness will wear down over time, and while that gradual decline in effectiveness occurs, it may seem extremely concerning that variants as wildly altered from the “original” coronavirus as Omicron are popping up across the globe. Yet vaccines are still proving to be largely effective, even against Omicron, as there are still many similarities among the spike proteins on the surface of different variants. That said, getting a booster shot will definitely help “re-jog” the memory of your T-lymphocytes and B-lymphocytes, and it is likely that as time goes on and coronavirus variants presumably become even more mutated, we may continue to need regular vaccinations to make sure our immune system is able to effectively recognize and destroy any new version of the coronavirus spike proteins.
BIBLIOGRAPHY
"COVID-19 Vaccines Work." Centers for Disease Control and Prevention, www.cdc.gov/coronavirus/2019-ncov/vaccines/effectiveness/work.html. Accessed 28 Apr. 2022.
"How Viruses Mutate and What It Means for a Vaccine." Pfizer Incorporated, www.pfizer.com/news/articles/how_do_viruses_mutate_and_what_it_means_for_a_vaccine#:~:text=As%20a%20virus%20replicates%2C%20its,virus'%20surface%20proteins%20or%20antigens. Accessed 28 Apr. 2022.
Maragakis, Lisa Lockard. "COVID-19 vs. the Flu." Johns Hopkins Medicine, www.hopkinsmedicine.org/health/conditions-and-diseases/coronavirus/coronavirus-disease-2019-vs-the-flu.
"Science Brief: Omicron (B.1.1.529) Variant." Centers for Disease Control and Prevention, www.cdc.gov/coronavirus/2019-ncov/science/science-briefs/scientific-brief-omicron-variant.html. Accessed 28 Apr. 2022.
"Understanding Viral Vector COVID-19 Vaccines." Centers for Disease Control and Prevention, www.cdc.gov/coronavirus/2019-ncov/vaccines/different-vaccines/viralvector.html. Accessed 28 Apr. 2022.
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