Explained: Two new vaccines, an oral pill against Covid-19, and how they work

What is the news?

India has approved two more Covid-19 vaccines, Corbevax and Covovax under emergency use authorization.It has also approved an antiviral drug, Molnupiravir to fight against COVID-19.

Must Read: What is Molnupiravir, the Covid-19 pill approved by India?

What is Covovax Vaccine?

Covavax is manufactured by Serum Institute of India(SII) and has been developed by US-based Novavax.

How does it work? It is a protein subunit vaccine that uses Recombinant Nanoparticle Technology (RNT).In this, harmless copies of the spike protein are grown in insect cells; the protein is then extracted and assembled into virus-like nanoparticles.

Novavax has also used an immune-boosting compound (adjuvant).The same technology is used in HPV and the Hepatitis B vaccine.

Efficacy: Based on phase trials, it has an efficacy of 96.4% against the original virus strain, 86.3% against Alpha and 89.7% efficacy overall.

What is Protein Sub-unit Vaccine and what are its drawbacks?

Protein subunit vaccines are made by isolating a piece of the actual virus. As fragments are used, there is no danger that these will multiply within the body. These pieces are expected to trigger an immune response that will hopefully prevent future infection. 

A downside to subunits is that because they contain only a part of the virus, they may miss certain characteristic signatures of the virus and the immune system may fail to recognise them. This problem is overcome by using adjuvant or booster shots. 

Another weakness is that these vaccines don’t infect the cells (like inactivated DNA or mRNA vaccines) and therefore doesn’t elicit the long-lasting immunity conferred by cells (or the T-cell response).

Source:This post is based on the article ‘Explained: Two new vaccines, an oral pill against Covid-19, and how they work’ published in Indian Express on 31^st Dec 2021.