Covishield immune responses against COVID-19 variants higher than Covaxin

Subject : Science and Technology

Context:

Neutralising antibody responses against COVID-19 variants of concern (VoC) are higher in Covishield recipients than those who took Covaxin, according to a new study.

About the study:

The study titled: Interim results from comparison of immune responses elicited by an inactivated and a vectored SARS-CoV-2 vaccine in seronegative and seropositive participants in India”, the study was published as a preprint on medRxiV.

Study findings:

Seropositive individuals (those who were already infected and had recovered from Covid before the first dose of vaccination) showed a higher response compared to seronegative individuals.
Covishield elicited immune responses of a higher magnitude and breadth than Covaxin in both Covid seronegative individuals and seropositive individuals.
While after the first and second dose of Covishield, concentration of antibodies increased in seronegative individuals by 2.1 and 7.6 fold, Covaxin did not attain such high levels of antibodies.
A large population has developed hybrid immunity.

Covishield

Covaxin

COVISHIELD:

It is the name given to an Oxford-AstraZeneca Covid-19 vaccine candidate which is technically referred to as AZD1222 or ChAdOx 1 nCoV19.

Produced By:

It is a version of the vaccine developed by the University of Oxford in collaboration with Swedish-British drugmaker AstraZeneca.
Serum Institute of India (SII) is the manufacturing partner in India.

Constituents and Action:

It is based on a weakened version of a common cold virus or the adenovirus that is found in chimpanzees.
This viral vector contains the genetic material of the SARS-CoV-2 spike protein (protrusions) present on the outer surface of the virus that help it bind with the human cell.
The body’s immune system is supposed to recognise this protein as a threat, and work on building antibodies against it.

Significance:

It had triggered an immune response in humans against the novel coronavirus in early trials and is considered to be one of the global frontrunners for the Covid-19 vaccine.

COVAXIN:

Produced By:

Developed by Bharat Biotech, Hyderabad in collaboration with the Indian Council of Medical Research’s National Institute of Virology, Pune

Constituents and Action:

It is an inactivated vaccine which is developed by inactivating (killing) the live microorganisms that cause the disease.
This destroys the ability of the pathogen to replicate, but keeps it intact so that the immune system can still recognise it and produce an immune response.
It is expected to target more than just the spike protein.
It also aims to develop an immune response to the nucleocapsid protein (the shell of the virus that encloses its genetic material).

Significance:

COVAXIN is more likely to work against newer variants of the virus, including the UK variant, as it contains immunogens (epitopes) from other genes in addition to those from Spike protein.
Immunogen is a stimulus that produces a humoral or cell-mediated immune response, whereas antigens are any substance that binds specifically to an antibody.
All immunogens are antigens, but all antigens may not be immunogens.
Approval of COVAXIN ensures India has an additional vaccine shield especially against potential mutant strains in a dynamic pandemic situation.