Guest Post | Immanuel Moses

The culprit behind COVID-19 disease 

The name “coronavirus” was just an unalarming word across the globe until late 2019. But the repercussions of the disease greatly threatened global health.

SARS-CoV-2 is the causative agent of coronavirus disease 2019 (COVID-19), a mild to severe infection of the respiratory system.

The genome size of the covid-19 virus ranges between 26 to 32 kilobases, thereby holding the credit as the longest genomic RNA virus.  

Key Operators of COVID-19 Virus 

The 4 structural proteins in the mechanism of action of COVID 19 virus are Nucleocapsid (N), Membrane (M), Spike (S) and Envelop (E) proteins including numerous non-structural proteins or NSP proteins.

The N protein being bound to the RNA genome of the virus, utilizes the human cell as warehouse for virus production. The M protein responsible for assembling the viral components is found in abundance on the viral membrane surface. S protein regulates the attachment and fusion mechanism of the virus to the host cell receptors. Thus, S protein paves the way for the virus into the host cell.

Despite its smaller size as a membrane protein, E protein plays an effective role in viral component assembly, host cell membrane permeability and virus-host interaction.  

Vaccine-The Need of the Hour 

Lack of a specific drug or vaccine was a great snag that perturbed the global community. Hence, devising a methodology to formulate appropriate drugs or vaccines is the pressing need of the hour.  Thanks to pioneering pharma companies, vaccines targeting SARS-CoV2 have now come up into the global market.

Covid-19 Vaccines Types 

All COVID-19 vaccines target at developing immunity against SARS-CoV-2 virus by activating an immune response to an antigen.  

Whole virus vaccines 

A few traditional vaccines have succeeded by altering the viral structure to inactivate and trigger only an immune response inside host’s body without causing a disease. When the host’s immune cells approach the deactivated viral antigens, they immediately confront and destroy them.

Following this, the memory cells furnish a snapshot of the viral structure and alert the immune system to generate antibodies that instantly target and destroy invading viral antigens in the future.  

Protein subunit vaccines 

Fragments of the virus are used instead of a complete virus in this method. The advantages of subunit vaccines include minimised side effects, stimulation of stronger immune response, low production cost and high availability.

To enhance quicker identification and higher visibility of the fragmented viral proteins by the immune cells, some chemical substances called as adjuvants are added. The general idea is to obtain a short piece of genetic code of the target virus, like SARS-CoV-2 virus. With these viral fragments, antigens are generated that trigger the immune response of the host. 

Viral Vector Vaccines  

This technology is currently explored by the University of Oxford/AstraZeneca against SARS-CoV2.  A harmless viral vector delivers the COVID 19 virus’ genetic code into the host cell that triggers the immune response without developing any disease.  The primary advantage of these vector-based vaccines is that they can trigger strong immune response without any adjuvants.

Nucleic Acid Vaccines     

The Moderna and Pfizer/BioNTech COVID-19 vaccines use this methodology by directly inserting genetic materials like mRNA into the host cells to produce antigens rather than using viral vectors to deliver the code.

The nucleic acid vaccines directly transfer the genetic material into cells with the help of a molecule to attach or by a “gene gun”. The merits of these vaccines are that they can be faster in action and low in production cost. With hundreds of COVID-19 vaccines now in development, it is likely that a mixture of different approaches will be needed to stop the global spread of COVID-19.

COVID-19 Vaccine Companies

Institute/CompanyVaccine name StatusType of vaccineDosageSuits people with
weak immune system
SinovacCoronaVacApproved in 7 countriesWhole virus (inactivated)2Yes
Bharath BiotechCovaxinApproved in IndiaWhole virus (inactivated)2Yes
Sinopharm (Wuhan)InactivatedApproved in China & UAE Whole virus (inactivated)2Yes
Medicago Inc.Plant-based VLPPhase 3 trial in Canada & USAWhole virus (virus-like particle)2Yes
NovavaxNVX-coV2373Five ongoing trials in 6 countriesProtein subunit2Yes
Serum Institute of India CovishieldApproved in 11 countriesViral vector2Yes
Oxford-AstraZenecaAZD1222Approved in 48 countriesViral vector1-2Yes
(depending on viral vector used)
CanSino BiologicsAd5-nCoVApproved in China, Pakistan & MexicoViral vector1-2Yes
(depending on viral vector used)
Johnson&JohnsonAd26.COV2.SOngoing 6 trials in 17 countriesViral vector1-2Yes
(depending on viral vector used)
Pfizer-BioNtechBNT162b2Approved in 60 countries including US & UKRNA2Yes
ModernamRNA-1273Approved in 38 countries including US & UKRNA2Yes


 In the beginning of December 2020, approximately 64 million positive cases and over one million deaths due to COVID-19 were confirmed worldwide. The COVID-19 pandemic has triggered psychological and socio-economic crisis globally.

Possible measures like initiation and implementation of COVID-19 testing, social distancing, usage of face masks and hand sanitizers to restrain the viral spread are inevitable; nevertheless, even such steps look purportless in the long run.  

Assessing the immune status and monitoring the immune memory duration from COVID-19 recovered patients may throw more light on designing a potential prophylactic therapy against COVID-19 virus.  

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