EXPLAINED: As India Clears SII's Covovax, Know What Is A Nanoparticle-Based Vaccine And How It Works

The Nanoparticle-based vaccine, Covovax, will be manufactured by Pune-based firm Serum Institute of India with the help of technology transfer from Novavax.

New Delhi: After an expert panel of the Central Drugs Standard Control Organisation (CDSCO) recommended granting emergency use authorisation (EUA) to the Serum Institute of India's (SII) COVID-19 vaccine Covovax and Biological E's vaccine Corbevax, with certain conditions, the Ministry of Health and Family Welfare granted the final nod Tuesday. 

Union Health Minister Mansukh Mandaviya announced on Twitter: "Further strengthening the fight against COVID-19, CDSCO & Ministry of Health and Family Welfare has given 3 approvals in a single day."

While CORBEVAX is an RBD protein subunit vaccine, SII’s Covovax is a nanoparticle-based vaccine. It will be manufactured by technology transfer from Novavax. Covovax is approved by the European Medicines Agency for conditional marketing authorisation, and has been granted emergency use listing by the World Health Organization.

What Is A Nanoparticle-Based Vaccine? 

A nanoparticle-based vaccine is one in which the receptor-binding domain (RBD), which is a part of the spike protein of SARS-CoV-2, is attached to a protein designed to form nanometre-sized protein particles, or nanoparticles, according to a study by the US National Institutes of Health (NIH), which was published in the journal, Nature. SARS-CoV-2 attaches itself to cells using the spike protein.

These nanoparticles could be composed of lipids, metal and non-metal inorganics, several polymers, and virus-like particles which have been tested for research, according to a study published by the National Center for Biotechnology Information (NCBI), NIH. Virus-like-particles (VLP) are self-assembling nanoparticles lacking infectious nucleic acid. 

How Does A Nanoparticle-Based Vaccine Work?

Nanoparticles help improve vaccine efficacy, by targeting desired antigen-presenting cells to improve immunisation strategies. They protect the antigen (foreign particle) from early proteolytic degradation (degradation of protein by hydrolytic enzymes), control antigen release, and facilitate antigen uptake.

Current vaccines cause cells in the body to make a version of the spike protein to elicit an immune response. Putting multiple copies of the RBD on nanoparticles enhances immune response, recent studies have found. The NIH researchers tested nanoparticle-based vaccines in monkeys and found that most of the monkeys had no virus in their lower respiratory tracts two days after exposure.

Nanoparticle-based vaccines contain a strand of genetic code that provides instructions for building a version of the spike protein, according to an article by the University of Pittsburgh Medical Center, US. Host cells build the protein when they see the genetic code.

The immune system begins building antibodies against the protein, which help the immune system fight the coronavirus. The body builds up an army of antibodies, which can fight off a Covid-19 infection before it causes disease.

Since mRNA is very fragile on its own, it would degrade in the body if it is injected simply as a strand. Hence, the genetic material is protected with a nanoparticle, which preserves the mRNA long enough to carry it into the body’s cells so that they can begin making the proteins.

The use of nanoparticles in vaccine formulations allows not only improved antigen stability and immunogenicity, but also targeted delivery and slow release, according to a article published in the journal, Elsevier.

The Covovax vaccine, which is based on Novavax, will work by teaching the immune system to make antibodies to the spike protein on SARS-CoV-2.