Know Your Vaccine: Covishield

These days, we have been hearing a lot about the shields developed by our scientific community to provide an effective defense against  the virus that almost brought down humanity to its knees. More than 29 million people in the country carry these shields already. Yes, you got the right idea, we are talking about the COVID vaccines that are finally available to us. In India, we have two such vaccines in use namely COVISHIELD and COVAXIN. In this article, we take you through the defense mechanism of one of these vaccines: Covishield, the efficacy of it, and the side-effects. 

Covishield has been developed by Oxford-AstraZeneca in partnership with the Serum institute of Pune, and was approved for use by the Government of India around two months back. Known as ChAdOx1 nCoV-19 or AZD1222, the vaccine produces the best result when administered in two doses a month apart. This vaccine uses the virus’s genetic instruction for building the spike protein as its base and is peculiar in that it stores the instructions in double-stranded DNA.

Development

The gene for the Coronavirus spike protein was added to another virus called Adenovirus, the viruses that typically cause colds or flu-like symptoms. The team used a  modified version of a chimpanzee adenovirus, known as ChAdOx1. AZD1222 is the result of decades of research on adenovirus-based vaccines. This modified form of virus can enter the cell but cannot replicate itself. There are two aspects that make this vaccine more rugged than its competitors and those are adenovirus’s tough protein coat, which helps protect the genetic material inside, and the storage of instructions in double-stranded DNA, which is not as fragile as RNA.

Defence Mechanism

Once the vaccine is delivered, the Adenoviruses bump into cells and get engulfed into a bubble and pulled into the cell where they travel to the nucleus after detaching themselves from the bubble. These Adenoviruses then transfer their DNA to the nucleus of the cell. The gene of the Coronavirus spike protein is then read by the nucleus and gets copied to a molecule called messenger RNA or mRNA. The mRNA  leaves the cell, and the cell starts assembling the spike proteins on its surface.

The immune system can effectively recognize these protruding spikes, and this particular vaccine causes the immune system to react more strongly to the spike proteins. After the cell dies, B cells come into action and bump into the spikes and lock onto them. These B cells are then activated by helper T cells and proliferate and pour put antibodies that target the protein spikes. 

Side Effects

Most common side effects include Pain or tenderness at the injection site, Headache, Tiredness, Muscle or joint aches, Fever, Chills, Nausea.

All in all, this vaccine provides an active defense against the novel Coronavirus with an efficacy of 62-90%, which is quite promising. Health centers across the country are delivering this vaccine to thousands of individuals everyday, and it seems to be working effectively, with minimal side effects, in providing protection against the virus.