Introduction
Vaccines are important to prevent and manage infectious diseases and are fundamental components of controlling the COVID-19 pandemic. Although mRNA vaccines are fairly new advancements in the vaccine world they have been in development and research for 30 years.[1] RNA vaccines such as Pfizer and Moderna have been pivotal during the COVID-19 pandemic due to the way they work. RNA COVID-19 vaccines generally work by introducing synthetically produced mRNA into cells, producing a spike protein that then initiates an immune response. BNT162b2 is the nucleotide-modified mRNA that Pfizer and Moderna use. In this essay, topics such as the principles of the COVID-19 RNA vaccine, the current development of COVID-19 RNA vaccines, clinical applications of COVID-19 vaccines as well as the advantages and disadvantages of COVID-19 RNA vaccines will be covered.
The principle of the COVID-19 RNA Vaccine
There are two types of mRNA vaccines: non-replicating RNA vaccines and self-replicating RNA vaccines. Non-replicating RNA vaccines are the simplest type of vaccine and include the mRNA code for the antigen. Self-replicating RNA vaccines also include mRNA coding for a viral antigen however it's more potent and the antigen is able to self-replicate resulting in high antigen expression levels. COVID-19 RNA vaccines are non-replicating RNA vaccines. [2,3]
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Typically, to trigger an immune response most vaccines will put an inactivated or dead germ into our bodies; however, mRNA vaccines insert synthetically mRNA into our bodies which then teaches our cells how to make a protein that triggers an immune response inside our bodies. [3,4] COVID-19 RNA vaccines are given in the upper arm muscle, The mRNA will enter the muscle cells and instruct the cells to produce a Spike protein. A spike protein is a protein that forms a large structure known as a spike projecting from the surface of an enveloped virus such as SARS-Cov-2, the virus that causes COVID-19. Therefore, the spike protein is found on the surface of the virus that causes COVID-19 and so after the protein piece is made, our cells break down the mRNA and remove it. Our cells then display the spike protein piece on their surface and our immune system recognizes the protein as foreign so begins to produce antibodies and activate other immune cells to fight off what it thinks is an infection. It does this by activating B (antibody-mediated) and T (cell-mediated) cells of the immune system.
Thus, our bodies will undergo the regular process to have the memory B cells ready for further infection from COVID-19 without the risk of getting very sick since our bodies will be prepared to fight off any live COVID-19 infections extremely quickly. Since these vaccines don't use the live virus, the vaccines cannot cause someone to contract COVID-19. Also, the mRNA created in our cells never enters the nucleus of the cell where our DNA is located so it cannot change or influence our genes.
This is only possible with the presence of lipid nanoparticles because without them the free mRNA in the body would be degraded quickly and won't last very long without the lipid nanoparticles.[3] The lipid nanoparticles help provide protection and transportation for the mRNA into the body by also aiding with intracellular delivery. It does this by coating the mRNA which then allows the mRNA to easily cross cell membranes into our body's cells. The lipid nanoparticles consist of a mixture of phospholipids, cholesterol, and ionizable lipids. The phospholipids and cholesterol aspects assist with structure and stabilizing the mRNA. [4,5] In BNT162b2 mRNA, the lipid nanoparticle around the mRNA strand is positively charged which stabilizes nucleic acids and increases their resistance to nuclease degradation which also helps them to be delivered to their target cells.
Clinical Trials and current development of COVID-19 RNA vaccines
As of March 2022, there are 3 RNA vaccines verified, including Pfizer, Moderna, and Takeda, however, of those 3 only Moderna and Pfizer are authorized for use. Moderna and Pfizer successfully passed Phase 3 clinical trials which happened in the Autumn of 2020. These vaccines were the first mRNA vaccines authorized for clinical use and were only developed in 3 months. The FDA gave a rare emergency authorization because of the ongoing COVID-19 pandemic.[6] Both vaccines are approved to use on adults however only Pfizer is authorized to be used on children aged 5-11 years of age. Vaccines undergo rigorous testing in Phase 1, and 3 trials before they are authorized for use, and organizations such as the World Health Organization (WHO) have detailed processes to determine whether a vaccine is safe and effective to use.[3] Even after successfully going through all three phases and being approved the vaccines are always monitored to ensure they're safe and effective with minimal side effects. As of right now, there are 35 approved vaccines for use across different countries and different vaccine types, as well as there, are currently 48 vaccines in phase 1, 70 in phase 2, and 68 in phase 3.
Phase 1 trials usually focus on ensuring the vaccine is safe to use in people, rather than on how effective it may be as a treatment for a given disease. [7,8] During this phase, different doses of the vaccine are given. Phase 2 trials generally assess the effectiveness of the vaccine so information about the vaccine's safety, side effects, and potential risks are also collected. Phase 3 trials test the results of earlier trials in much larger groups of people and gather additional information on the effectiveness and safety of the vaccine. Vaccines must pass all 3 clinical trial phases to be used on the general public.
Normally, this process took years or even decades sometimes to make sure there was enough evidence in favor of a new vaccine but of course, due to the urgency of the COVID-19 pandemic, clinical trials had to be accelerated as the development of the COVID-19 vaccine was vital. This was achieved because coronaviruses were already being researched since they've been around since the SARS outbreak in 2002 also combined with a lot of funding led to quick clinical trials that also went through the regular safety measures. [9]
In Clinical trials, the most common side effects following the vaccination with COVID-19 RNA Vaccines included mild symptoms of pain at the injection site, headache, and fatigue. These symptoms usually resolve after a few days. However, there were a few reports of myocarditis and pericarditis that occurred within 14 days after vaccination more often after the second dose and in younger males aged 12-30 years of age however, the majority of these cases have been relatively mild, and resolved quickly with conservative therapy and rest. [10]
Clinical Applications of COVID-19 RNA Vaccines
On the 31st of December 2020, a clinical trial occurred with 43,548 participants where 43,448 had injections. 21,720 had BNT162b2 and 21,728 with a placebo (these participants were unvaccinated). This randomized trial assessed the safety, efficacy, and immunogenicity of the BNT162b2 vaccine in adolescents and teenagers. [11] It was discovered that only 8 cases of COVID-19 occurred within 7 days after the 2nd dose of BNT162b2 but there were 162 cases of COVID-19 amongst the placebo group of participants. Additionally, among 10 severe cases of COVID-19 across all participants, 9 of them happened in the placebo group. From this study, BNT162b2 was revealed to be 95% effective in preventing COVID-19 in adolescents and teenagers.
The majority of side effects that occurred in the BNT162b2 group were short-term mild to moderate pain at the injection site, fatigue, and headaches but subsided quickly. This study, therefore, highlights the effectiveness of using mRNA vaccines to combat COVID-19 as, ‘through 6 months of follow-up, BNT162b2 has a favorable safety profile and was highly efficacious in preventing COVID-19’.[11]
Advantages of RNA vaccine
There are many advantages to using RNA vaccines to treat and help prevent the spread of COVID-19. As previously mentioned, RNA vaccines are not made with the live virus so are non-infectious since you cannot contract COVID-19 from these vaccines. [3,12] In addition, the RNA does not integrate itself into the nucleus of the cell so leaves our DNA unaltered. Furthermore, neither the lipid nanoparticles nor spike protein persists. Early clinical trial results indicate that these vaccines generate a reliable immune response and work well in healthy individuals as there are very few side effects. It was also 95% effective in protecting against COVID-19.
Production of RNA vaccines is laboratory-based, so the process can easily be regulated and upscaled which can then allow for quick responses to infection such as what happened with the coronavirus pandemic. This is because the RNA is made from a DNA template which only takes around a week to make a full batch. This in turn can also make RNA vaccines more cost-effective and cheaper to produce globally and more standardized for future development of different vaccines for different viruses using the same process as the COVID-19 vaccine.
Disadvantages of RNA vaccine
There aren't many disadvantages of the COVID-19 RNA vaccine as all vaccines undergo strict standards of safety, quality, and effectiveness. However, since the coronavirus outbreak came on so suddenly the clinical trial processes were significantly sped up, so the vaccine didn't undergo as thorough a clinical trial as other vaccines, which could have unforeseen side effects in the future. Therefore, longer trial studies are needed to learn more about RNA vaccines although as previously mentioned the World Health Organization is always regulating vaccines to make sure they are safe and effective. Although a myriad of testing has occurred to ensure these new mRNA vaccines are safe to use, it's still a new field of medicine that needs to be regulated constantly to maintain safety and effectiveness. Storage is also a problem with RNA vaccines since they need to be frozen or refrigerated due to mRNA being highly labile. This creates a new challenge for low-income countries as storage alone could be quite expensive since Pfizer needs to be stored at -70°C and Moderna between -50°C and -15°C. [3,12]
Conclusion
It has been demonstrated the importance of the new mRNA vaccines with how effective they are in preventing the spread of COVID-19 as shown to be 95% effective. It's also important to note how many advantages RNA vaccines have over other vaccines as being quick and easy to produce is vital in combating the COVID-19 pandemic. Furthermore, considering Pfizer and Moderna have been authorized for use for almost 2 years now demonstrates their effectiveness as well as being the main vaccines used at the moment which has also cleared most doubts people had initially with the new mRNA vaccines. The safety and efficacy of new RNA COVID-19 vaccines are always being regulated and with more research and more clinical trials taking place, we can hopefully keep improving the vaccines and hopefully return to a world without COVID-19.
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