Comparison of Covid-19 vaccine
Last Updated 3 February 2021. Cellspect Co., Ltd.
After suffering a terribly awful 2020 of Covid-19 pandemic, scientists embarked on a race to produce safe and effective coronavirus vaccines in record time. People now finally see some hope of returning to normal life as good news of Covid-19 vaccine gradually coming out. Up to date, several Covid-19 vaccines have been authorized for emergency use in various countries. Vaccines work by exposing healthy people to parts of a pathogen, allowing human immune system to develop the cells and proteins necessary for fighting off the pathogen when they come across the real disease. The Covid-19 vaccines currently administered globally can be roughly divided into three categories:
1. RNA vaccines (Pfizer/BioNtech and Modena)
2. adenovirus vaccines (Oxford-AstraZeneca and Gamaleya)
3. inactived/dead coronavirus (Sinopharm)
Below is a quick guide to the COVID-19 vaccines now mainly in use around the world.
An RNA vaccine contains mRNA which, when introduced into a tissue to cause the cells to build the foreign protein and stimulate an adaptive immune response. The delivery of mRNA is achieved by a co-formulation of the molecule into lipid nanoparticles which protect the RNA strands and helps their absorption into the cells. RNA vaccines are a relatively new type of vaccines and draw public interests because they can be developed in a laboratory using readily available materials. Advantages of RNA vaccines include good safety (since there are no live components, there’s no risk of the vaccine triggering disease), reliability, and that it’s relatively simple to manufacture. Actually, mRNA vaccines have been studied before for flu, Zika, rabies, and cytomegalovirus (CMV). However, mRNA is extremely fragile and if not handled properly it can fall apart. The storage and long-distance shipping will be a big problem for RNA vaccines. Another fact is that this type of vaccine has never previously been licensed for humans.
Adenovirus vector vaccines
These vaccines are examples of non-replicating viral vector vaccines, using an adenovirus shell containing DNA that encodes a SARS-CoV-2 protein. Adenovirus-vectored vaccines are the other technology that has been close behind the mRNA-based vaccines in clinical testing. The biggest advantage of Adenovirus vaccines is that scientists have been using this technology in the lab for decades. The process of inserting genes into the adenovirus vectors is well developed so it can also be done pretty quickly. Moreover, the storage condition for adenovirus vaccines is much easier than RNA vaccines. Notedly, previous exposure to the vector might reduce the effectiveness.
Inactivated virus vaccines
Inactivated vaccines consist of virus particles that have been grown in culture and then are killed using a method such as heat or formaldehyde to lose disease producing capacity, while still stimulating an immune response. the advantages of an inactivated virus vaccine include the fact its technology is well established, it is suitable for people with compromised immune systems, and it’s relatively simple to manufacture.
The US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) set a cutoff of 50% as the efficacy required to approve a COVID‑19 vaccine. Currently, most Covid-19 vaccines show better efficacy than WHO’s recommendation. Other than efficacy, safety has been a top priority. Vaccine developers report side effects that include pain at the injection site, fever, muscle aches, fatigue and headaches, mostly lasting about a day or two. These are normal side effects after inoculation. So far, none of the vaccine trials have reported any serious safety concerns and safety data are continuously reviewed by the FDA and expert panels. But according to the CDC, at this time, anyone who has a severe allergy (e.g., anaphylaxis) to any of the Pfizer/BioNTech vaccine ingredients should not receive this vaccine. One more issue is that the vaccine's side-effects are rare and usually mild, but they could include fever and nausea, which could be dangerous in very ill and frail patients. Some death after Covid-19 vaccination was reported and the new guidance says doctors should evaluate each individual patient to determine whether the benefits of vaccination outweigh the risks of any potential side effects.
Coronavirus Vaccine Tracker: The New York Times: https://www.nytimes.com/interactive/2020/science/coronavirus-vaccine-tracker.html
U.S. Food and drug administration: https://www.fda.gov/
World Health Organization: WHO https://www.who.int/
Centers for Disease Control and Prevention: https://www.cdc.gov/
COVID-19 vaccine – Wikipedia: https://ourworldindata.org/
BBC News: https://www.bbc.com/news
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