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Pfizer's mRNA Vaccine: A Breakthrough in Vaccine Development

Updated: Nov 24, 2020

On Tuesday (11/10/20), Pfizer/ BioNTech just announced their candidate vaccine was more than 90% effective in preventing infection in volunteers. Mumps vaccine was the fastest vaccine that has ever been developed, and that took 4 years. With this new candidate, we might be able to start Coronavirus vaccination as early as 2021.

How does Pfizer's COVID-19 vaccine work? And what does this mean for our effort in combating COVID-19 Pandemic? To understand the current development of COVID-19 vaccines, we first need to under how our immune system works. In this article, we will break down the key components of the immune system, explain how vaccines initiate immunity against pathogens and discuss why Pfizer's mRNA Vaccine is a breakthrough that might change the way we respond to pandemics and infectious diseases.

Two Phases of Immune Responses

A typical immune response launches its defense in two phases; the innate response and the adaptive response. The innate response is fast and non-specific but very crucial as it allows the immune system to prepare for a second and more specific attack -- the adaptive response.

The innate immune system consists of multiple levels of protection; the physical and chemical barriers such as skin, mucus, or stomach acid are the first layer of protection. The second layer of protection is our inflammatory response. Tissue redness, swelling, and fever during infection are examples of the inflammatory response. Innate immunity has been developed and evolved to keep us safe from various toxins and infectious agents, including bacteria, fungi, viruses, and parasites found in our surrounding environment.

The second phase of attack -- the adaptive immune response -- is more specific to its target and kicks in about a week later. The specificity and amplification of immune response are due to the development of disease-specific antibodies. Antibodies are molecules that can recognize, flag the invading agents for destruction, or prevent them from entering healthy cells. Antibodies for a specific virus are developed 2-3 weeks after the initial infection and remain present in the body. They also act as a memory of a particular pathogen so that our immune system can recognize and launch attacks against the virus immediately the second time around.

Graphic Source: https://www.who.int/emergencies/diseases/novel-coronavirus-2019/covid-19-vaccines/how-do-vaccines-work

The World's First Effective Coronavirus Vaccine

Vaccines help develop immunity by imitating an infection without causing a full-blown immune response costly to the body. There are different ways in which researchers can obtain this result (view infographic below).

A conventional vaccine contains weakened or inactive parts of the pathogen (antigens). These selective pathogenic elements will trigger some part of the immune system leading to the body developing immunity against the pathogen without provoking a full immune response. The challenge lies in designing, building/ isolating such pathogen-like element, and delivering it safely inside the body. It can take years to create a clinically approved vaccine. Mumps vaccine is the fastest vaccine that has ever been developed, and it took four years.

In recent years, there has been a new class of vaccines, called RNA and DNA vaccines. RNA vaccines are cheaper, faster to produce, and easier to be distributed. RNA vaccine has never been done before, and there are no DNA or RNA vaccines currently in use.

Conventional vaccines require designing and building pathogen-like elements or organisms so that the cell can register it as a threat without going into “under attack” mode.

RNA vaccines omit this step and leave that work to the host cells. Instead of injecting a weakened or inactive part of the pathogen (antigen), the RNA vaccine introduces an mRNA sequence, which acts as a set of instructions for the cells to produce the disease-specific antigens themselves. By having the cells produce the viral parts themselves, mRNA cuts out the year-long manufacturing process in making traditional vaccines. mRNA vaccines are easier and quicker to make, leading to a significantly shorter production and distribution time than conventional vaccines.

On Tuesday, November 10th, Pfizer/BioNTech announced preliminary results that suggest their vaccine was more than 90 percent effective. Pfizer/BioNTech Vaccine is an mRNA vaccine that coded for the signature spike proteins found on the coronavirus's surface. Although this gives us hope that vaccine developments are on the right track, much is still unknown about the effectiveness of this vaccine and how it will be distributed. If Pfizer/BioNTech vaccine is clinically approved, it will be the first-ever RNA vaccine developed. mRNA vaccines will revolutionize vaccine development and our response to future pandemics.



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