After the Brazilian and South African strains of SARS-CoV-2 (coronavirus) were reported in India, domestic vaccine makers are gearing up to test the efficacy of their respective shots against these two variants in a laboratory setting.
Pankaj Patel, chairman of Cadila Healthcare — which has a vaccine candidate ZyCoV-D in phase 3 clinical trials in India and another measles vector-based vaccine at the cusp of clinical trials — said it was not possible to test the efficacy of the vaccine candidates against the mutant strains in clinical trials as the disease was not endemic in India.
There are not enough number of cases with the South African and Brazilian strains in the country to check the efficacy. So far, India has recorded four Covid-positive cases with the South African variant, and one with the Brazilian variant.
Patel said that the company would conduct in-vitro (outside a living organism) or laboratory tests to see if the vaccines worked against the mutant strains. In case its candidates do not show efficacy against these new mutant strains, the company plans to work on a new generation of vaccines.
Since Cadila Healthcare's vaccine (ZyCoV-D) is based on DNA-plasmid technology, Patel expected that next-generation vaccines could be made rather fast.
Conventional active vaccines are made of a killed or weakened form of the infectious agent. DNA plasmid vaccine is a relatively new approach where part of DNA containing the genes for the antigen is injected. The body then learns to develop an immune response against the antigen, and when the actual pathogen attacks, the body can generate specific antibodies against it.
The Indian Council of Medical Research has already said that the Pune-based National Institute of Virology (NIV) was in the process of isolating and culturing the South African variant in its laboratory.
The ICMR plans to draw serum samples from people who have already received the vaccines in India to test in a lab if they can generate neutralising antibodies against the two latest variants that have entered India. Bharat Biotech, the makers of Covaxin which has already got restricted emergency use nod from the drug regulator, had done the same to check the efficacy of their vaccine against the UK strain.