COVID-19 Vaccine: Techniques used in Various Clinical Trials

Different Types of Covid-19 Vaccines Prepared In Clinical Trials

A record speed has been observed in the development of the COVID-19 vaccine since the outbreak of the Coronavirus pandemic globally. Countries all over the world are investing hugely in the development or import of the vaccine. More than 150 different types of Covid-19 vaccines are on trial using different techniques. 

Daily Tactics Guru here explains the difference between these vaccines and how they can protect us against the Coronavirus disease

There are various vaccine candidates in progress simultaneously, for COVID-19 than for any other infectious disease ever. And they share the common aim of providing immunity against the deadly virus. Some companies are also making efforts to create a barrier in the transmission of the disease. They may achieve this by stimulating an immune response towards the antigen found on the virus. The antigen of Coronavirus typically possesses a crown-like structure that contains spikes on the outer surface. These spikes help the virus invade the human cells easily. 

Some Major Categories of Covid-19 Vaccines


Most of the Covid-19 vaccines made traditionally are based on this technique. The virus as a whole is used to activate an immune response.

This can be done by two different methods.

The virus responsible for causing a particular disease is weakened and injected into the cells in Live attenuated vaccines. In this condition, the virus does not prove out to be harmful but can still replicate itself. As soon as the body encounters the virus, the cells initiate the process of formation of antibodies. 

Inactivated vaccines work on the technique of injecting the viruses whose genetic material has been destroyed. Thus, lose the capacity to replicate itself, but still have the ability to trigger an immune response. 

The cells coming in contact with the dead virus release antibodies. As the human cells have a unique characteristic of remembering the antigen and the response. Therefore, when the cells come in contact with the living virus, they get a reminder of the initial response which they experienced before. And produces the same antibodies to fight against the causative agents. 

Well-established technologies and pathways are used for regulatory approval. But live attenuated ones have the risk of causing disease in people who have weak immune systems. Both require careful cold storage. 


The disease causing pathogens are fragmented into different segments of protein. These fragments of protein subunits are used in subunit vaccines to trigger an immune response from the cells. This technique has minimum risk of side effects but it results in a weak immune response in comparison to others. And thus to boost the immune response they often require adjuvants.


These vaccines use either RNA or DNA to instruct the cells to prepare the antigen. The genetic material is introduced into human cells. Protein factories of the cells are used by the genetic material to prepare the antigen within the cell in large quantities. This antigen will in turn activate the cells to create a strong immune response. 

These nucleic acid vaccines are easy to make and cost effective. 

However, to the disadvantage of humans, no such vaccines are not being licensed for human use. But efforts to remove the hurdles in their regulatory approval are also on the way. 

These Covid-19 vaccines need to be kept at an ultra-low temperature which is a huge challenge in itself particularly the underdeveloped countries.


Viral Vector vaccines are also basically based on the same technique as the RNA vaccines. But they use a harmless virus instead to deliver the instructions to the cells regarding the production of the antigen. This harmless virus is different from the one the vaccine is targeting. 

The other difference between the nucleic acid vaccines and viral vector vaccines is in the machinery to make the antigen. RNA vaccines or DNA vaccines use the original cellular machinery of the body or tissue to produce the antigen using the instructions given in order to trigger an immune response. Whereas Viral vector vaccines do not hijack the original cellular machinery but mimic natural viral infection. And thus produce a stronger immune response. 

Daily Tactics Guru has discussed different COVID-19 vaccines produced by different countries and organizations in another article. Do not forget to read about them

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Stay Happy and Stay Safe… 

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