Covaxin: How Bharat Biotech plans to boost immunity

Adjuvants may be added to a vaccine to produce more antibodies and longer lasting immunity thus minimising the dose of antigen needed.

Hyderabad based Bharat Biotech, whose Covid-19 vaccine candidate Covaxin is one of the leading candidates from India, will use adjuvant from Kansas based ViroVax for its vaccine to boost immune response and longer lasting immunity.

Vaccines typically use adjuvants to improve the immune response. Adjuvants are pharmacological or immunological agents that improve the immune response of a vaccine.

It may be added to a vaccine to produce more antibodies and longer lasting immunity thus minimising the dose of antigen needed.

An antigen is any substance that causes our immune system to produce antibodies against it.

It can be any substance like chemicals, viruses, bacteria that the immune system does not recognise and tries to fight off.

ViroVax's alhydroxiquim II adjuvant will be used in Covaxin which is an inactivated Sars-CoV-2 virus vaccine.

The inactivated virus is formulated with ViroVax’s adjuvant to produce the vaccine candidate.

Bharat Biotech is conducting phase II clinical trials in healthy volunteers for Covaxin.

Krishna Ella, chairman and managing director of Bharat Biotech, said, “There is critical need for development and availability of adjuvants that elucidate mechanisms of action inducing greater antibody responses to vaccine antigens, thus resulting in long-term protection against pathogens.

"Adjuvants also enhance the sustainability of the global vaccine supply on account of their antigen-sparing effect.”

He further added that the widely used adjuvant aluminium hydroxide in the development of Sars-CoV-2 vaccines is known to induce Th2 based response.

However, Th2 based response has a theoretical risk of vaccine associated enhanced respiraroty diseases (VAERD or ADE).

"We have used Imidazoquinoline class of adjuvants (TLR7/8 agonists), which are known to induce Th1 based response which further reduces the risk of ADE (Anti-Body Dependent Enhancement).”

In the preclinical studies and animal challenge models (Syrian Hamster and Rhesus Macaques) Bharat Biotech has shown that Covaxin induced Th1 based response.

In response to the Covid-19 pandemic, ViroVax also received supplemental funding for the development of subunit vaccine constructs for the prevention of COVID-19, and for the discovery and development of therapeutics for treating Covid-19.

ViroVax is evaluating a subunit vaccine candidate and has identified potential antiviral therapeutics.

It is currently in the process of testing the efficacy of these compounds.

Photograph: Courtesy, Bharat Biotech