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A Comparative Study of Eight Classes of COVID 19 Vaccines

A comparative study of eight classes of COVID 19 vaccines are done.  There is an ongoing global effort to develop an effective vaccine against COVID-19. There are eight types of COVID 19 vaccines. Research community loves RNA and DNA based vaccines, but history has shown success in non-nucleic-acid vaccines. Here, we analysed vaccines in an open mind. We explained the strength and weakness of each class of COVID 19 vaccine from multiple angles.

The critical bottleneck for developing the most effective and early COVID 19 vaccine is age-old research protocols and standards. Unless we throw them into the dustbin and find out new ways, Humanity will face much bigger blows.  

For machine learning projects, in our Compassionate AI Lab, we focus on those classes types of COVID 19 vaccines to fight against Coronavirus. AI and machine learning has a huge role to play in shortening the vaccine development timeline. The best thing about this technology is that it bypasses many of the traditional steps to vaccine discovery and development. Vaccine development strategies are also linked to the life cycle of the COVID-19 viruses

Each type of vaccine offers unique benefits and challenges. The basic principle of vaccine is imitating a real viral infection and inducing a protective immune response in the body. More than 190 vaccines for COVID 19 are being developed against SARS-CoV-2 virus by research teams across the world. They are in different stages of their development. Here, we discussed the eight types of vaccines.  

Eight Types of Vaccines to Fight Against COVID-19

Eight Types of Vaccines to Fight Against COVID-19

COVID 19 Vaccines A Brief Introduction

The successful development and use of vaccines for covid 19, can save millions of lives.   Now, more than 100 groups all over the world working on a coronavirus vaccine. One of the major reasons for the delay in COVID  19 vaccine is giving excessive priorities to the gene-based vaccines. Gene-based, RNA and DNA vaccines have many ethical issues moreover, there is never been a gene-based vaccine approved by the Food and Drug Administration.  

Prior to the 1980s, non-gene-based vaccines were developed for protection against disease-causing by the microorganisms and there was a great levels of success. On the other hand, Gene-based vaccines are much-hyped and driven by huge funds but no success. The FDA has yet to approve any DNA or RNA vaccines for human use. Now,  big companies taking COVID-19 as a big opportunity to push gene-based vaccines.

To do a comparative study of the COVID-19 vaccine strategies and to know the driving force behind the delay in the vaccines and the drugs, we have to analyse them with multiple viewpoints. 

Live Attenuated or Weakened Virus (LAV)

A disease-causing virus or bacterium is attenuated and weakened in a laboratory so it cannot cause disease. In contrast to inactivated virus vaccines, these vaccines, also whole viruses, are live to elicit a more robust immune response but weakened to reduce virulence. These vaccines are often cheap to produce and generally give good immunity against infection because they can induce both cell-mediated and antibody-mediated immune responses.

The use of live attenuated or killed whole organism-based vaccines had enormous success in the control and eradication of several severe human infectious diseases, including smallpox, polio, measles, mumps, rubella, and animal infectious diseases, such as classic swine fever, cattle plague, and equine infectious anaemia.

The key concerns about LAV applications include the potential to cause disease in immunocompromised individuals and the possibility of reversion to a virulent form due to the back-mutation, the acquisition of compensatory mutations, or recombination with circulating transmissible wild-type strains

Inactivated Virus Vaccine

Like the attenuated vaccines, inactivated virus vaccines contain whole virus particles, but in this case, without live genetic material. The RNA or DNA of the virus is usually destroyed chemically or by heat, leaving the immunogenic elements unaltered. In general, inactivated virus vaccines do not provide as strong of an immune response as live attenuated virus vaccines, so additional doses of the vaccine may be needed to get a strong enough immune response. Still, they may be safer for some people. These vaccines elicit an antibody-mediated immune response but usually not a cell-mediated one. It can be used in people that may not be able to use a live attenuated virus vaccine (e.g., those who are immuno-compromised).

Replicating Viral Vector Vaccine

This replicating viral vector vaccine involves putting a gene for a viral protein into a different virus (one that will not cause illness but can replicate). Replication of the viral vector also produces copies of the viral protein, which triggers an immune response to that protein. Replicating viral vector vaccines use a replicating viral vector that has been modified to produce coronavirus proteins in the body.  Examples include ebola and dengue vaccines.

Non-Replicating Viral Vector Vaccine

This approach is similar to replicating viral vector vaccines in that a viral gene is added to a different, non-replicating, virus and delivered to the vaccine recipient.  Non-replicating viral vectors – typically have additional genetic alterations compared with replicating vectors, with essential viral replication genes deleted from the vector. No approved product of this kind has resulted to date.

Protein Subunit Vaccine

Rather than introducing whole viruses to an immune system, a fragment of the virus is used to trigger an immune response and stimulate immunity. Subunit vaccines are made using the antigenic proteins of the virus without any of the genetic material, which means they cannot replicate inside the body. Because of this, they are considered very safe to use. However, the immune response induced by subunit vaccines is not as strong as for some other types, although this may be improved by using adjuvants. These vaccines may also require several doses to be effective in the long term. Examples include the subunit vaccines against hepatitis B and shingles. 

Virus-Like Particle Vaccine

Virus-like particle (VLP) vaccines closely resemble viruses but are non-infectious because they contain no viral genetic material. Since VLPs cannot replicate, they provide a safer alternative to attenuated viruses. Virus-like particles are the synthetic protein shells that mimic the structure of a virus, including its antigenic components, without any of the genetic material inside. They have been shown to induce strong immune responses because they preserve the antigen pattern seen on live viruses.  Examples include the HPV vaccine.

Non-viral delivered nucleic acids are categorized as DNA or RNA according to their type of 5-carbon sugar. For a classical vaccine, the antigen is introduced in the body to produce an immune response. However, in the case of DNA- or RNA-based vaccines, no antigen is introduced, only the RNA or DNA containing the genetic information to produce the antigen.

DNA-Based Vaccine

DNA-based vaccines work by inserting a genetically engineered blueprint of viral gene(s) into small DNA molecules (called plasmids) for injection into vaccinated people. Cells take in the DNA plasmids and follow their instructions to build viral proteins, which the immune system recognizes as foreign, triggering the immune response that protects against the disease. DNA vaccines are efficient at generating T-cell responses. 

However, the main disadvantage of the DNA vaccine is that the injected DNA will integrate into one of the human chromosomes inside the cell, which may cause other problems. Although DNA vaccines are promising and with shown safety, well-tolerability and immunogenicity, DNA vaccines were characterized by suboptimal potency in early clinical trials.

RNA-Based Vaccine

Similar to DNA vaccines, these experimental vaccines provide immunity through the introduction of genetic material (RNA). RNA vaccines can also be potentially developed more quickly and efficiently than other vaccines. These mRNA vaccines are based on an engineered viral genome containing the genes encoding the RNA replication machinery. In contrast, the structural protein sequences are replaced with the gene of interest (GoI), and the resulting genomes are referred to as replicons.

These vaccines are named self-amplifying mRNA and are capable of directing their self-replication, through the synthesis of the RNA-dependent RNA polymerase complex, generating multiple copies of the antigen-encoding mRNA, and express high levels of the heterologous gene when they are introduced into the cytoplasm of host cells, in a way that mimics production of antigens in vivo by viral pathogens, triggering both humoral and cellular immune responses.  However, no RNA vaccines have been approved for human use.


The struggle to develop a COVID 19 vaccine is on a scale we have never seen before. Vaccine researchers around the world are trying hard and putting extraordinary efforts to help end the pandemic as soon as possible. However, there are many other issues. Comparatively, minimal effort is given for non-nucleic-acid based vaccines. There are many ethical issues in Gene-based vaccines. On the other hand, whole virus vaccines are useful with known side effects. We are looking for safe and effective vaccines for COVID-19 very fast, and the effort should be in the proper direction so that we can get the result fast.

Cite This Article



Ray, Amit. (2020). A Comparative Study of Eight Classes of COVID 19 Vaccines. [online] www.amitray.com. 2020 Jul 11 Available at: https://amitray.com/a-comparative-study-of-eight-classes-of-covid-19-vaccines/ [Accessed 27-Jul-2021]


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Ray, Amit. (2020 Jul 11). A Comparative Study of Eight Classes of COVID 19 Vaccines. Retrieved from https://amitray.com/a-comparative-study-of-eight-classes-of-covid-19-vaccines/


Ray, Amit. A Comparative Study of Eight Classes of COVID 19 Vaccines. www.amitray.com. 2020 Jul 11, https://amitray.com/a-comparative-study-of-eight-classes-of-covid-19-vaccines/ Accessed 27-Jul-2021


Ray, Amit. "A Comparative Study of Eight Classes of COVID 19 Vaccines." www.amitray.com. https://amitray.com/a-comparative-study-of-eight-classes-of-covid-19-vaccines/ Accessed 27-Jul-2021