Different institutions and medical organizations are working to develop COVID-19 vaccines all around the globe. Scientists have already introduced different types of vaccines while 170 vaccines are still in trial. Why are there so many vaccines and which factor differentiates them?
Since 2019, a common disease has disrupted the system of the whole world. Yes, you guessed it right. The sudden outbreak of “coronavirus” has made everybody house-arrested which has resulted in massive economic stress globally. Therefore, there are more vaccine candidates in the pipeline for COVId-19 than ever before in medical history.
The core objective of this effort is to achieve an “Immunity to the Coronavirus”. However, many scientists are also trying to cease the transformation of this disease anymore. For this purpose, they are stimulating an immune response to an antigen (a molecule found on the coronavirus). In the case of COVID-19, we refer to antigen as the spike protein found on the top surface of the virus. This antigen is mainly responsible to invade human cells and cause infections.
Types Of Coronavirus Vaccines:
Currently, scientists have classified the COVID-19 vaccines in clinical trials in 4 categories.
- WHOLE VIRUS.
- PROTEIN SUBUNIT.
- VIRAL VECTOR.
- NUCLEIC ACID (RNA AND DNA).
Some of the vaccines are capable to inject the antigen into the body. While others try to use the body’s own cells to make the viral antigen in order to develop immunity in the body.
Here are the details about the four major categories of the COVID-19 vaccine.
1. Whole Virus:
Many conventional vaccines use whole viruses to boost the immune response of the human body. It can happen with 2 approaches;
Live attenuated vaccines:
It uses a weak form of the virus that doesn’t harm the human body. Although, it keeps replicating without causing any illness.
This vaccine contains viruses that have a destroyed genetic material. Hence, it is not capable to replicate. Still, it can trigger the immune response of the human body.
Both these types follow the same mechanism to establish pathways for regulatory approval. Also, both of these vaccines use very well-established technology to pass from the approval procedures. The only difference between these vaccines is that live attenuated vaccines have more potential to cause illness in people with weak immune systems.
Also, it is quite difficult to use these vaccines in low-resource countries because it requires careful cold storage. However, people with compromised immune systems can get these vaccines. Also, they need to make sure to keep these vaccines in favorable cold storage.
2. PROTEIN SUBUNIT
The basic ingredient of these vaccines is the pieces of the pathogen. These pathogens are usually used in the form of fragmented proteins. This special composition allows them to trigger an immune response in the human body.
Also, it reduces the risk of side effects that could be caused by the whole virus vaccines. While considering this factor, we can also understand that this vaccine may also have a weak immune response. Therefore, it also requires additional adjuvants that assist the vaccine to boost the immune response. For example, we have the hepatitis B vaccine as an existing submit vaccine.
3. NUCLEIC ACID
The nucleic acid vaccine requires genetic material either RNA or DNA. in this way, it becomes able to provide instructions to the cells and they start making antigens. Especially, in the case of COVID-19, it is all about those viral protein spikes on the surface.
Once the genetic material of these weakened coronaviruses gets into the human cells then it starts using the protein factories. In this way, it produces antigens that trigger an immune response.
The most prominent advantage of these vaccines is that they are easy to produce and cost less. Therefore, they are relatively cheaper than other vaccines. Since it enables our cells to produce antigens and in larger quantities.
There is only one drawback that there is no DNA or RNA vaccine that is licensed for human use. Hence, it can cause more complications with regulatory approval. Moreover, RNA vaccines also require to be kept in an ultra-cold temperature i.e. -70C or lower. Therefore, it can also create challenges for resource-deficient countries to create a favorable environment for vaccine storage. Particularly, low or middle-income countries can’t afford to use any equipment to store any RNA vaccine.
4. VIRAL VECTOR
Viral vector vaccines also work with the same mechanism. They contain genetic material of the coronavirus that they use to pass instructions to the cells. They are different from nucleic acid vaccines because they use harmless viruses. These viruses are totally different from the target virus. They use harmless viruses to pass messages to the human cells.
Adenovirus is a type of virus that is used as viral vector vaccines. This virus is responsible for the common cold in humans. It has the ability to hijack human cells. So it can boost our immune response and productivity of antigens with those instructions.
The viral vector is also capable of mimicking natural viral infection. In this way, it triggers a strong immune response. However, since there is a chance that those people who are already infected from the coronavirus can be used as vectors. Therefore, their body cells have already built an immunity against the virus and they can make the vaccines less effective.
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