Understanding the Science Behind COVID-19 Vaccination
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Chapter 1: Introduction to COVID-19 Vaccines
As the pandemic continues, numerous experimental vaccines targeting COVID-19 are undergoing clinical trials. Moderna, the developer of the mRNA-1273 vaccine, has announced that it may be accessible to a limited group of individuals this fall.
Phase 1 trials for mRNA-1273 commenced recently. This innovative vaccine aims at the proteins present on the surface of the coronavirus. It operates by injecting synthetic mRNA sequences into the patient’s body. These sequences enable the recipient's immune system to create proteins that mimic those associated with COVID-19, which then circulate and trigger an immune response. Researchers are optimistic that this response will lead to immunity against the virus.
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Section 1.1: The Mechanics of mRNA Vaccines
Administering mRNA vaccines to stimulate protein production presents significant challenges, as this process contradicts the body's natural biological mechanisms. Within cells, mRNA acts as a messenger between the genetic code in DNA and the proteins that are synthesized. After being produced in the cell nucleus, mRNA travels to the cytoplasm, where ribosomes translate it into proteins. Typically, mRNA is only stable long enough for this translation before it is degraded.
Introducing mRNA from outside the cell contradicts the central dogma of molecular biology. Generally, any external genetic material is recognized as a foreign entity and swiftly degraded, which poses a substantial hurdle for the mRNA-1273 vaccine.
Derreck Rossi from the Harvard Stem Cell Institute and a co-founder of Moderna has discovered a method to improve the stability of externally introduced mRNA. RNA consists of four basic nucleotides—adenine, guanine, cytosine, and uracil (A, G, C, U)—linked together. By substituting uracil with pseudouracil, Rossi's team was able to extend the lifespan of the mRNA long enough to ensure the expression of the intended proteins (Rossi D, 2010).
Subsection 1.1.1: Overcoming Membrane Barriers
Another major challenge for mRNA vaccines is the transfer of mRNA across the cell's outer membrane. The plasma membrane functions like a protective barrier, selectively permitting certain molecules to enter or exit the cell. Since mRNA cannot easily penetrate this barrier, vaccines require assistance. Various technologies can couple vaccine mRNA with compounds that facilitate entry into cells, such as protamines, lipids, and nanoparticles (Kaufmann K, 2016).
Section 1.2: Upcoming Trials and Future Distribution
Results from the Phase 1 trials for mRNA-1273 are expected in the coming weeks, and the research team remains optimistic about a limited release of the vaccine.
Who Will Receive the Vaccine?
Should the trials yield successful outcomes, the expedited distribution of mRNA-1273 will likely be limited to healthcare professionals. This distribution could occur under the FDA Emergency Use Authorization, which fast-tracks the approval of medical treatments during emergencies.
The mRNA-1273 vaccine is still awaiting results from its ongoing Phase 1 clinical trial, which is currently being conducted in Washington State. For further details on these trials, more information can be found here.
Chapter 2: The Future of Vaccination
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